[core] Link earcut.hpp and rapidyaml

[sruon]

I affirm:

• I understand that if I do not agree to the following points by completing the checkboxes my PR will be ignored.
• I understand I should leave resolving conversations to the LandSandBoat team so that reviewers won't miss what was said.
• I have read and understood the Contributing Guide and the Code of Conduct.
• I have tested my code and the things my code has changed since the last commit in the PR and will test after any later commits.

What does this pull request do?

2 new libraries:

• earcut.hpp for defining and sampling arbitrary polygons. To be used for roam areas, spawn points and eventually fishing zones.
  • This is what Eden is using, didn't investigate alternatives too much. Made by MapBox, header only and simple interface.
  • Actual design/usage TBD, depends on YAML to be introduced first.
• rapidyaml for parsing and loading upcoming YAMLs
  • Header only, not overly fond of the interface but it gets the job done and it vastly outperformed alternatives by several orders of magnitude in my tests.
  • I have the design more or less done but I need to do a POC before sharing

Steps to test these changes

Nothing is changing... yet