Feat: Gitlab connector (#12248)

### What problem does this PR solve?

Feat: Gitlab connector
Fix: submit button in darkmode

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

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Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

common/data_source/config.py

@@ -55,6 +55,8 @@ class DocumentSource(str, Enum):
     BOX = "box"
     AIRTABLE = "airtable"
     ASANA = "asana"
+    GITHUB = "github"
+    GITLAB = "gitlab"
 
 class FileOrigin(str, Enum):
     """File origins"""