Add auto-assignee for new PRs

[OrlinVasilev]

Add new action to auto assign the author of the PR as assignee and 2 of the maintainers as reviewers.
That will help us to improve time to review for PRs!

Signed-off-by: OrlinVasilev [email protected]

Thank you for contributing to Harbor!

Comprehensive Summary of your change

Issue being fixed

Fixes #(issue)

Please indicate you've done the following:

• Well Written Title and Summary of the PR
• Label the PR as needed. "release-note/ignore-for-release, release-note/new-feature, release-note/update, release-note/enhancement, release-note/community, release-note/breaking-change, release-note/docs, release-note/infra, release-note/deprecation"
• Accepted the DCO. Commits without the DCO will delay acceptance.
• Made sure tests are passing and test coverage is added if needed.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed in website repository.

[codecov]

Codecov Report

Merging #17753 (99fab7c) into main (4fb0a19) will decrease coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main   #17753      +/-   ##
==========================================
- Coverage   66.58%   66.53%   -0.05%     
==========================================
  Files         998      997       -1     
  Lines      106908   106721     -187     
  Branches     2597     2589       -8     
==========================================
- Hits        71185    71010     -175     
+ Misses      31806    31789      -17     
- Partials     3917     3922       +5     

Flag	Coverage Δ
unittests	66.53% <ø> (-0.05%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/lib/cache/util.go	73.07% <0.00%> (-15.39%)	⬇️
...src/app/shared/services/message-handler.service.ts	18.42% <0.00%> (-13.16%)	⬇️
src/core/auth/authenticator.go	48.81% <0.00%> (-9.45%)	⬇️
...tegration/tag-retention/tag-retention.component.ts	21.71% <0.00%> (-9.05%)	⬇️
src/portal/src/app/shared/units/shared.utils.ts	22.22% <0.00%> (-8.34%)	⬇️
...es/vulnerability/vulnerability-config.component.ts	58.51% <0.00%> (-4.45%)	⬇️
src/common/utils/email/mail.go	35.05% <0.00%> (-3.10%)	⬇️
src/server/v2.0/handler/base.go	68.75% <0.00%> (-1.47%)	⬇️
...tegration/immutable-tag/immutable-tag.component.ts	62.50% <0.00%> (-1.36%)	⬇️
src/lib/config/userconfig.go	68.91% <0.00%> (-0.65%)	⬇️
... and 18 more

[wy65701436]

lgtm

[yanji09]

LGTM