chore(codeowners): set sdk_team as code owners (#148)

## Summary

Adds a root `CODEOWNERS` with `* @rudderlabs/sdk_team` so chore PRs
(Dependabot merges, CI fixes) auto-request review from the whole SDK
team and any member's approval unblocks them. No CODEOWNERS existed
before. Brings this repo in line with the other SDK repos already
migrated.

## Changes

- `CODEOWNERS` (new): `* @rudderlabs/sdk_team`
- `.github/ISSUE_TEMPLATE/bug_report.md`: clears the hardcoded
individual assignee (`itsdebs` → `[]`), matching the pattern used in the
other SDK repos

## Testing

Config-only change — verify on the next chore PR that review is
auto-requested from `sdk_team` (the open Dependabot PRs #128 and #141
can serve as the verification case once this merges). New bug reports
should open unassigned.

## Screenshots

No UI changes in this PR.

## Notes

Fixes
[SDK-5173](https://linear.app/rudderstack/issue/SDK-5173/set-sdk-team-as-code-owners-in-rudder-sdk-java).
No breaking changes or migration steps required.

Author: SKannaniOS

.github/ISSUE_TEMPLATE/bug_report.md

@@ -3,7 +3,7 @@ name: Bug report
 about: Create a report to help us improve
 title: "BUG : <Title>"
 labels: bug, open source
-assignees: itsdebs
+assignees: []
 ---
 
 **Describe the bug**

CODEOWNERS

@@ -0,0 +1 @@
+* @rudderlabs/sdk_team