feat: add a github action to self-assign the issue

[Phoenix500526]

Problem

Currently，contributors can't self-assign issues in this repo. They have to leave a comment asking a committer to assign the issue to them.

Desired outcome

We can add a github action to enable self-assignment. Leave a "take" comment to self-assign the issue, and a "untake" comment to unassign.

Alternatives or workarounds

No response

[Phoenix500526]

Hi, @jackwener @Astro-Han . The two comments above are coordinated spam containing links to sexually explicit content. Could you block both accounts? I've already reported them to GitHub Trust & Safety.

[Astro-Han]

Blocked the two spam comments! Thanks for reporting them.

[0xMudit]

I'd like to work on this issue.

Proposed approach

1. Create .github/workflows/self-assign.yml using �ctions/github-script@v7
2. Listen for issue_comment events matching ake / untake keywords
3. Use the GitHub Issues API to assign/unassign the commenting user

This is a simple, self-contained workflow with no external dependencies beyond the official �ctions/github-script action.

[Phoenix500526]

I'd like to work on this issue.

Proposed approach

1. Create .github/workflows/self-assign.yml using �ctions/github-script@v7
2. Listen for issue_comment events matching ake / untake keywords
3. Use the GitHub Issues API to assign/unassign the commenting user

This is a simple, self-contained workflow with no external dependencies beyond the official �ctions/github-script action.

@0xMudit , Thanks, but I've already open a PR to fix it, so you don't need to waste your time and tokens.