chore: improve event and custom metadata docs

[yordis]

closes #89

[yordis]

Not sure how doc changes caused CI to failed 😭

[coveralls]

Pull Request Test Coverage Report for Build 1bc62fda82702725e7b96caffd77c5f72020b55d-PR-90

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 99.577%

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Totals
Change from base Build da513877522564c5236e97ee2fcfd12acc7fd6a0:	0.0%
Covered Lines:	706
Relevant Lines:	709

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💛 - Coveralls