Add documentation for MWK, UGX, and XOF mobile money accounts (#245)

## Summary
- Add external account creation examples for Malawi (MWK), Uganda (UGX),
and West Africa (XOF) mobile money
- Add phone number validation patterns for the new currencies in the
best practices section
- Syncs documentation with recent OpenAPI changes from commits a292f0b
and f4d545d

## Context
Recent OpenAPI schema changes added support for three new African mobile
money currencies:
- **MWK_ACCOUNT**: Malawi mobile money (+265 phone format)
- **UGX_ACCOUNT**: Uganda mobile money (+256 phone format)
- **XOF_ACCOUNT**: West African CFA franc mobile money (Senegal +221,
Benin +229, Ivory Coast +225)

The `mintlify/snippets/external-accounts.mdx` documentation was missing
examples for these account types.

## Test plan
- [ ] Verify the MDX renders correctly in Mintlify dev server
- [ ] Confirm phone number regex patterns match OpenAPI schema
definitions
- [ ] Check that all new tabs appear in the external accounts
documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: EC2 Default User <ec2-user@ip-192-168-240-144.us-west-2.compute.internal>
Co-authored-by: Peng Ying <peng@lightspark.com>
Co-authored-by: greptile-apps[bot] <165735046+greptile-apps[bot]@users.noreply.github.com>

Author: 6 people

mintlify/snippets/external-accounts.mdx

@@ -468,6 +468,114 @@ curl -X POST 'https://api.lightspark.com/grid/2025-10-13/customers/external-acco
 </Note>
 </Tab>
 
+<Tab title="Malawi">
+**MWK Mobile Money**
+
+```bash cURL
+curl -X POST 'https://api.lightspark.com/grid/2025-10-13/customers/external-accounts' \
+  -H 'Authorization: Basic $GRID_CLIENT_ID:$GRID_CLIENT_SECRET' \
+  -H 'Content-Type: application/json' \
+  -d '{
+    "currency": "MWK",
+    "platformAccountId": "mw_mobile_001",
+    "accountInfo": {
+      "accountType": "MWK_ACCOUNT",
+      "phoneNumber": "+265991234567",
+      "provider": "AIRTEL",
+      "beneficiary": {
+        "beneficiaryType": "INDIVIDUAL",
+        "fullName": "Chimwemwe Banda",
+        "birthDate": "1993-03-18",
+        "nationality": "MW",
+        "address": {
+          "line1": "Kamuzu Procession Road",
+          "city": "Lilongwe",
+          "postalCode": "00100",
+          "country": "MW"
+        }
+      }
+    }
+  }'
+```
+
+<Note>
+  Phone number must be in format `+265XXXXXXXXX` (9 digits after country code). Providers: `AIRTEL` or `TNM`.
+</Note>
+</Tab>
+
+<Tab title="Uganda">
+**UGX Mobile Money**
+
+```bash cURL
+curl -X POST 'https://api.lightspark.com/grid/2025-10-13/customers/external-accounts' \
+  -H 'Authorization: Basic $GRID_CLIENT_ID:$GRID_CLIENT_SECRET' \
+  -H 'Content-Type: application/json' \
+  -d '{
+    "currency": "UGX",
+    "platformAccountId": "ug_mobile_001",
+    "accountInfo": {
+      "accountType": "UGX_ACCOUNT",
+      "phoneNumber": "+256701234567",
+      "provider": "MTN",
+      "beneficiary": {
+        "beneficiaryType": "INDIVIDUAL",
+        "fullName": "Nakato Sarah",
+        "birthDate": "1990-07-25",
+        "nationality": "UG",
+        "address": {
+          "line1": "Kampala Road 45",
+          "city": "Kampala",
+          "postalCode": "00100",
+          "country": "UG"
+        }
+      }
+    }
+  }'
+```
+
+<Note>
+  Phone number must be in format `+256XXXXXXXXX` (9 digits after country code). Providers: `MTN` or `AIRTEL`.
+</Note>
+</Tab>
+
+<Tab title="West Africa">
+**XOF Mobile Money (Senegal, Benin, Ivory Coast)**
+
+```bash cURL
+curl -X POST 'https://api.lightspark.com/grid/2025-10-13/customers/external-accounts' \
+  -H 'Authorization: Basic $GRID_CLIENT_ID:$GRID_CLIENT_SECRET' \
+  -H 'Content-Type: application/json' \
+  -d '{
+    "currency": "XOF",
+    "platformAccountId": "xof_mobile_001",
+    "accountInfo": {
+      "accountType": "XOF_ACCOUNT",
+      "phoneNumber": "+221781234567",
+      "provider": "ORANGE",
+      "beneficiary": {
+        "beneficiaryType": "INDIVIDUAL",
+        "fullName": "Mamadou Diallo",
+        "birthDate": "1988-11-12",
+        "nationality": "SN",
+        "address": {
+          "line1": "Avenue Cheikh Anta Diop",
+          "city": "Dakar",
+          "postalCode": "10000",
+          "country": "SN"
+        }
+      }
+    }
+  }'
+```
+
+<Note>
+  Supported countries and phone formats:
+  - Senegal (+221): `+221XXXXXXXXX` (9 digits after country code)
+  - Ivory Coast (+225): `+225XXXXXXXXXX` (10 digits after country code)
+  - Benin (+229): `+229XXXXXXXX` or `+229XXXXXXXXX` (8–9 digits after country code)
+</Note>
+</Tab>
+
 <Tab title="Canada">
 **CAD Bank Transfer**
 
@@ -710,6 +818,16 @@ if (!/^\+260\d{9}$/.test(zmwPhoneNumber)) {
 if (!/^\+250\d{9}$/.test(rwfPhoneNumber)) {
   throw new Error("Invalid Rwandan phone number");
 }
+if (!/^\+265\d{9}$/.test(mwkPhoneNumber)) {
+  throw new Error("Invalid Malawian phone number");
+}
+if (!/^\+256\d{9}$/.test(ugxPhoneNumber)) {
+  throw new Error("Invalid Ugandan phone number");
+}
+// West African (XOF): Senegal (+221), Ivory Coast (+225), Benin (+229)
+if (!/^\+(221\d{9}|225\d{10}|229\d{8,9})$/.test(xofPhoneNumber)) {
+  throw new Error("Invalid West African phone number");
+}
 ```
 
 </Accordion>