libyaml & pyyaml fuzzers

[TheZ3ro]

This PR adds:

• 2 new fuzzers for libyaml covering two APIs of the emitter component
• 1 new fuzzer for pyyaml covering part of the Scanner class
• an updated dict file for both projects

[github-actions]

TheZ3ro is a new contributor to projects/pyyaml. The PR must be approved by known contributors before it can be merged. The past contributors are: hunsche, cclauss, TheShiftedBit, fmeum, catenacyber
TheZ3ro is a new contributor to projects/libyaml. The PR must be approved by known contributors before it can be merged. The past contributors are: arthurscchan, hunsche, perlpunk, ingydotnet, alex, rjotwani, cvediver, Dor1s, ssbr (unverified), sigmavirus24 (unverified), inferno-chromium (unverified), mikea (unverified)

[DavidKorczynski]

How much gain do we receive from the libyaml harness? It also looks quite comprehensive, how sure are you that this matches a threat model of the project and it won't produce potential false positives?