docs: update code owners

[mkbreuningIOHK]

Description:

• Code owners: the content editor will be automatically added to any PR related to markdown files
• Code owners: update by adding Todor Kolev (still not a member it seems though)
• Pull request template: add the link to the contributing guideline
• Pull request template: modify to be able to check / uncheck boxes without editing the comment

Checklist:

• My PR follows the contribution guidelines of this project
• My PR is free of third-party dependencies that don't comply with the Allowlist
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked the PR title to follow the conventional commit specification

[github-actions]

# npm audit report

follow-redirects  <=1.15.5
Severity: moderate
follow-redirects' Proxy-Authorization header kept across hosts - https://github.com/advisories/GHSA-cxjh-pqwp-8mfp
fix available via `npm audit fix`
node_modules/follow-redirects

1 moderate severity vulnerability

To address all issues, run:
  npm audit fix

[github-actions]

# npm audit report

follow-redirects  <=1.15.5
Severity: moderate
follow-redirects' Proxy-Authorization header kept across hosts - https://github.com/advisories/GHSA-cxjh-pqwp-8mfp
fix available via `npm audit fix`
node_modules/follow-redirects

1 moderate severity vulnerability

To address all issues, run:
  npm audit fix

[mkbreuningIOHK]

@elribonazo , can you review this PR: this will fix the PR template checkbox as well :)

[github-actions]

Lines	Statements	Branches	Functions
	70.06% (1823/2602)	56.59% (717/1267)	72.65% (542/746)

JUnit

Tests	Skipped	Failures	Errors	Time
408	2 💤	0 ❌	0 🔥	1m 0s ⏱️