chore: add community standards (CoC, contributing, security, templates)

Adds the seven files needed to pass the GitHub Community Standards checklist:

- CODE_OF_CONDUCT.md (Contributor Covenant 2.1)
- CONTRIBUTING.md (scope, dev setup, tests, PR rules; points users at
  feder-cr/firefox-stealth for C++/spoofing issues)
- SECURITY.md (private vuln reporting via GH advisories or email,
  out-of-scope items redirected to firefox-stealth / Mozilla)
- .github/ISSUE_TEMPLATE/bug_report.yml
- .github/ISSUE_TEMPLATE/feature_request.yml
- .github/ISSUE_TEMPLATE/config.yml (disables blank issues, links to
  security advisories, firefox-stealth, and discussions)
- .github/PULL_REQUEST_TEMPLATE.md

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,11 @@
+blank_issues_enabled: false
+contact_links:
+  - name: Security vulnerability
+    url: https://github.com/feder-cr/invisible_playwright/security/advisories/new
+    about: Report a security issue privately. Do NOT open a public issue.
+  - name: Bug in the patched Firefox itself (canvas / WebGL / fonts / WebRTC / etc.)
+    url: https://github.com/feder-cr/firefox-stealth/issues
+    about: Spoofing/fingerprint bugs belong in the firefox-stealth repo.
+  - name: Question or general discussion
+    url: https://github.com/feder-cr/invisible_playwright/discussions
+    about: For usage questions, ideas, and chat. Bugs and features still go in issues.