Add template for updating source connector type (#9430)

Author: tuliren

.github/ISSUE_TEMPLATE/source-connector-type.md

@@ -0,0 +1,26 @@
+---
+
+name: Source Connector Type
+about: Add a new type or update an existing type in source connector
+title: '[EPIC] Add new type / update <type-name> in source connector <connector-name>'
+labels: area/connectors, needs-triage
+assignees: ''
+
+---
+  
+## Summary
+(Choose one of the two below.)
+- [ ] Support new type <type-name>
+- [ ] Update existing type <type-name>
+
+## TODOs
+(Complete the TODOs based on the instruction, and convert each bullet point with the `[Issue]` tag into an issue.)
+- [ ] [Issue] Add a new destination acceptance test (DAT) test case for this type.
+- List every destination below, either update the destination to suppor this type, or override its DAT to bypass the new test case.
+  - [ ] Example: [Issue] support <type-name> in destination bigquery
+- [ ] [Issue] Make sure every destination can pass the new DAT test case.
+  - Even if a destination does not need to support this type, its DAT should not break.
+- List every source that should support this type below.
+  - [ ] Example: [Issue] support <type-name> in source github
+
+## Desired Timeline