feat: add Abseil to V8 deps (#751)

Refs: nodejs/node-v8#211
Refs: v8/v8@fa7521e

Author: targos

lib/update-v8/constants.js

@@ -30,6 +30,10 @@ const zlibIgnore = `!/third_party/zlib
 /third_party/zlib/contrib/tests
 /third_party/zlib/google/test`;
 
+const abseilIgnore = `!/third_party/abseil-cpp
+/third_party/abseil-cpp/.github
+/third_party/abseil-cpp/ci`;
+
 export const v8Deps = [
   {
     name: 'trace_event',
@@ -82,5 +86,11 @@ export const v8Deps = [
     repo: 'third_party/ittapi',
     gitignore: '!/third_party/ittapi',
     since: 81
+  },
+  {
+    name: 'abseil',
+    repo: 'third_party/abseil-cpp',
+    gitignore: abseilIgnore,
+    since: 121
   }
 ];