[docs] Add changelog based on “Keep a Changelog” (#80)

Reviewed-on: https://codeberg.org/superseriousbusiness/masto-fe-standalone/pulls/80
Co-authored-by: Zoë Bijl <code@moiety.me>
Co-committed-by: Zoë Bijl <code@moiety.me>

Merge pull request #2422 from ClearlyClaire/glitch-soc/merge-upstream

Merge upstream changes

Merge branch 'main' into glitch-soc/merge-upstream

Bump version to v4.2.0 (#27017)

Merge pull request #2419 from ClearlyClaire/glitch-soc/merge-upstream

Merge upstream changes

Merge branch 'main' into glitch-soc/merge-upstream

Conflicts:
- `README.md`:
  Upstream changed their README, we have a completely different one.
  Kept our version.

Update changelog (#26992)

Merge pull request #2416 from ClearlyClaire/glitch-soc/merge-upstream

Merge upstream changes

Merge branch 'main' into glitch-soc/merge-upstream

Bump version to v4.2.0-rc2 (#26974)

Merge pull request #2406 from ClearlyClaire/glitch-soc/merge-upstream

Merge upstream changes up to 6273416292090b2f6bfda33f070cea325a1759df

Merge commit 'b90383d07388fe8513e59a6deb1a2391146c6561' into glitch-soc/merge-upstream

Bump version to v4.2.0-rc1 (#26916)

Merge pull request #2396 from ClearlyClaire/glitch-soc/merge-upstream

Merge upstream changes

Merge commit 'f80f426c57d5a5e1d289372ef7c323741d27c768' into glitch-soc/merge-upstream

Bump version to v4.2.0-beta3 (#26753)

Merge pull request #2392 from ClearlyClaire/glitch-soc/merge-upstream

Merge upstream changes into glitch-soc

Merge commit '072112867b9a3ec090ad2c92d6363b47b2265d74' into glitch-soc/merge-upstream

Merge pull request #2383 from ClearlyClaire/glitch-soc/merge-upstream

Merge upstream changes

Fix changelog wording and missing items (#26638)