allow customizing styles (#25)

Author: dwwoelfel

README.md

@@ -16,3 +16,127 @@ See the [example repo](https://github.com/OneGraph/graphiql-explorer-example) fo
 ![Preview](https://user-images.githubusercontent.com/476818/51567716-c00dfa00-1e4c-11e9-88f7-6d78b244d534.gif)
 
 [Read the rationale on the OneGraph blog](https://www.onegraph.com/blog/2019/01/24/How_OneGraph_onboards_users_new_to_GraphQL.html).
+
+
+## Customizing styles
+
+The default styling matches for the Explorer matches the default styling for GraphiQL. If you've customized your GraphiQL styling, you can customize the Explorer's styling to match.
+
+### Customizing colors
+
+The Explorer accepts a `colors` prop as a map of the class names in GraphiQL's css to hex colors. If you've edited the GraphiQL class names that control colors (e.g. `cm-def`, `cm-variable`, `cm-string`, etc.) use those same colors in the colors map. The naming of the keys in the colors map tries to align closely with the names of the class names in GraphiQL's css (note that the Explorer can't just apply the classes because of conflicts with how the css file styles inputs).
+
+Example style map:
+
+```javascript
+<Explorer colors={{
+  keyword: '#B11A04',
+  // OperationName, FragmentName
+  def: '#D2054E',
+  // FieldName
+  property: '#1F61A0',
+  // FieldAlias
+  qualifier: '#1C92A9',
+  // ArgumentName and ObjectFieldName
+  attribute: '#8B2BB9',
+  number: '#2882F9',
+  string: '#D64292',
+  // Boolean
+  builtin: '#D47509',
+  // Enum
+  string2: '#0B7FC7',
+  variable: '#397D13',
+  // Type
+  atom: '#CA9800',
+}} />
+```
+
+### Customizing arrows and checkboxes
+
+The explorer accepts props for setting custom checkboxes (for leaf fields) and arrows (for object fields).
+
+The props are `arrowOpen`, `arrowClosed`, `checkboxChecked`, and `checkboxUnchecked`. You can pass any react node for those props.
+
+The defaults are
+
+arrowOpen
+```javascript
+  <svg width="12" height="9">
+    <path fill="#666" d="M 0 2 L 9 2 L 4.5 7.5 z" />
+  </svg>
+```
+
+arrowClosed
+```javascript
+  <svg width="12" height="9">
+    <path fill="#666" d="M 0 0 L 0 9 L 5.5 4.5 z" />
+  </svg>
+```
+
+checkboxChecked
+```
+  <svg
+    style={{marginRight: '3px', marginLeft: '-3px'}}
+    width="12"
+    height="12"
+    viewBox="0 0 18 18"
+    fill="none"
+    xmlns="http://www.w3.org/2000/svg">
+    <path
+      d="M16 0H2C0.9 0 0 0.9 0 2V16C0 17.1 0.9 18 2 18H16C17.1 18 18 17.1 18 16V2C18 0.9 17.1 0 16 0ZM16 16H2V2H16V16ZM14.99 6L13.58 4.58L6.99 11.17L4.41 8.6L2.99 10.01L6.99 14L14.99 6Z"
+      fill="#666"
+    />
+  </svg>
+  ```
+
+checkboxUnchecked
+```
+  <svg
+    style={{marginRight: '3px', marginLeft: '-3px'}}
+    width="12"
+    height="12"
+    viewBox="0 0 18 18"
+    fill="none"
+    xmlns="http://www.w3.org/2000/svg">
+    <path
+      d="M16 2V16H2V2H16ZM16 0H2C0.9 0 0 0.9 0 2V16C0 17.1 0.9 18 2 18H16C17.1 18 18 17.1 18 16V2C18 0.9 17.1 0 16 0Z"
+      fill="#CCC"
+    />
+  </svg>
+```
+
+### Customizing the buttons to create new operations
+
+You can modify the styles for the buttons that allow you to create new operations.
+
+Pass the `styles` prop when you create the component. It's an object with two keys, `explorerActionsStyle` and `buttonStyle`.
+
+Example styles map:
+```javascript
+<Explorer
+  styles={{
+    buttonStyle: {
+      fontSize: '1.2em',
+      padding: '0px',
+      backgroundColor: 'white',
+      border: 'none',
+      margin: '5px 0px',
+      height: '40px',
+      width: '100%',
+      display: 'block',
+      maxWidth: 'none',
+    },
+
+    explorerActionsStyle: {
+      margin: '4px -8px -8px',
+      paddingLeft: '8px',
+      bottom: '0px',
+      width: '100%',
+      textAlign: 'center',
+      background: 'none',
+      borderTop: 'none',
+      borderBottom: 'none',
+    },
+  }}
+/>
+```