docs: Add yara-language-server to known migrations

Hi!

We just finished the migration to v1.0.0, so I thought it would be useful for others to include it into known migrations docs :) .

PS: I hope I got the .rst syntax right

Code review checklist (for code reviewer to complete)

[x] Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
[x] Title summarizes what is changing
[x] Commit messages are meaningful (see this for details)
[/] Tests have been included and/or updated, as appropriate
[x] Docstrings have been included and/or updated, as appropriate
[x] Standalone docs have been updated accordingly
[/] CONTRIBUTORS.md was updated, as appropriate
[/] Changelog has been updated, as needed (see CHANGELOG.md)