feat(*): adding templates, stale and contributing artifacts

[ChronosSF]

No description provided.

[Copilot]

Pull request overview

Adds GitHub community/automation artifacts to standardize contributions and triage for the documentation repo, including stale automation, PR checklist guidance, issue templates, and a consolidated contributing guide.

Changes:

• Add a scheduled workflow to mark stale issues/PRs with a status: stale label.
• Introduce PR and issue templates to guide documentation changes and bug reports.
• Add a comprehensive .github/CONTRIBUTING.md with xplat MDX authoring guidance (tokens, <Sample>, <PlatformBlock>, <ApiLink>, images).

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
.github/workflows/pr-stale.yml	Adds a scheduled actions/stale workflow for inactivity labeling.
.github/PULL_REQUEST_TEMPLATE.md	Adds a PR checklist template for doc contribution quality gates.
.github/ISSUE_TEMPLATE/docs-task.md	Adds a documentation task/enhancement issue template.
.github/ISSUE_TEMPLATE/docs-issue.md	Adds a documentation issue/bug report template.
.github/CONTRIBUTING.md	Adds contributor guidance, including xplat MDX patterns and workflow conventions.

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[dobromirts]

ref - https://github.com/IgniteUI/igniteui-angular/blob/master/.github/ISSUE_TEMPLATE/bug_report.yml