feat(docs): emit/event docs

[leohhhn]

Description

This PR adds docs for emit/event. It adds reference docs, and a section in effective Gno. More practical examples will be added to Gno By Example.

Closes: #2003

Contributors' checklist...

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests
• Added new benchmarks to generated graphs, if any. More info here.

[zivkovicmilos]

I find it strange that you didn't mention the required PR on the docs repo anywhere:
gnolang/docs.gno.land#29

Please fix the failing PR on that repo, it can't even build because of invalid IDs.
We can see what to do about this one after that

Also, please add adequate labels to this PR 🙏

[leohhhn]

Hey @zivkovicmilos,

I find it strange that you didn't mention the required PR on the docs repo anywhere:

I've linked this PR in the docs.gno.land repo PR, so the connection should be visible (right above your comment).

Please fix the failing PR on that repo, it can't even build because of invalid IDs.

Due to the setup that we currently have with the documentation infra, it is currently not possible to build or preview the documentation on the docs.gno.land repo - which is why the CI is red on the mentioned PR. Specifically, this is because the CI on the other repo fetches the monorepo master branch and tries to build the files, but since this PR here has not been merged yet (and thus the files are missing, hence the 'invalid ID' error), the build will fail.

Currently, the only way to get the CI fixed on the other repo is to merge content here first. This PR is ready for review - please convert it back to the correct status 🙏

Also, please add adequate labels to this PR 🙏

Added the docs label - I was under the impression that we have a bot doing that for us.

[notJoon]

I left some minor things, but overall it's well written. 👍