Automatically convert todo comments in code to the issues

[php-coder]

Follow-up to: #1595

Currently I'm investigating the idea to supply a similar automation by myself:

• when code gets submitted to master branch, github action is spinned up:
  • it clones a repository
  • runs pdd
  • collects all todos
  • commits (with information about an original commit) the results (pdd.xml + todos-in-code.tsv) into a separate branch named generated-todos; no commit if there were no new todos discovered
  • it also creates the issues for new todos. To link a puzzle with related issue, the todos-on-github.tsv is used. That file is also committed to the generated-todos branch
• IDEA: close an issue when a puzzle gets removed (resolution: extracted to Close an issue or post a comment when a puzzle got removed from code #1616)
• IDEA: remove a link when an issue gets closed manually (resolution: extracted to Post a comment when issue got closed without removing a puzzle #1617)
• IDEA: consider import of https://www.0pdd.com/xml?name=php-coder/mystamps (with closed puzzles) (resolution: it doen't worth it)

Checklist:

• Generate pdd.xml
• Generate todos-in-code.tsv
• Generate a mapping between puzzles ids and existing issues
• Deal with incorrect comments (with trailing --> or */)
• Create new issues for todos without mapping
• Cleanup
  • remove gh1595_extract_todos branch
  • remove generated-todos-test branch
• Document
  • put a workaround for pdd/wiremock back
  • create pdd-xml-to-json.sh as pdd doesn't support JSON output (+pdd issue)
  • modify comments to avoid having next lines in a title
  • workaround: 2 search queries because github doesn't support OR
  • workaround: possible collisions because GitHub doesn't support exatch match
  • pdd: workaround for trailing --> (pdd gh111)