Git-machete

- added: full chain of PRs (and not just a link to the base PR) is added to/updated in PR description by `git machete github create-pr`/`retarget-pr`/`restack-pr` (suggested by mjgigli)
- fixed: in the unlikely case of a cycle between GitHub PRs, `git machete github checkout-pr` aborts with an error rather than falling into an infinite loop
- fixed: when checking out longer PR chains, `git machete github checkout-prs` prints out all checked out branches correctly

- improved: if neither `.git/info/description` nor `.github/pull_request_template.md` is present, `git machete github create-pr` now uses message body of the first unique commit as PR description (suggested by kamaradclimber)
- added: `machete.github.forceDescriptionFromCommitMessage` git config key that forces `git machete github create-pr` to use message body of the first unique commit as PR description (suggested by kamaradclimber)

- fixed: `Cannot parse Link header` error in `git machete github` subcommands when there are more than 100 PRs in the given repository (reported by domesticsimian)
- fixed: if `.git/machete` doesn't exist, `git machete add <branch>` adds both current branch and the newly-added `<branch>` (not just the latter)

- added: `--removed-from-remote` flag to `git machete slide-out` (contributed by raylu)
- added: `--title` flag to `git machete github create-pr` that allows for setting PR title explicitly (suggested by mjgigli)
- added: `--with-urls` flag to `git machete github anno-prs` and `machete.github.annotateWithUrls` git config key that allow for adding the URL of the PR to the annotations (contributed by guyboltonking)
- added: `--yes` flag to `git machete github create-pr` so that the user isn't asked whether to push the branch (suggested by mkondratek)
- deprecated: `git machete clean` and `git machete github sync`; use `github checkout-prs --mine`, `delete-unmanaged` and `slide-out --removed-from-remote` instead
- fixed: PR author is now always added to annotation if different from current user (contributed by guyboltonking)

- added: `git machete github create-pr` adds a comment linking the PR to its base PR; `github retarget-pr` keeps that comment up to date (suggested by guyboltonking)
- added: new subcommand `git machete github restack-pr`, which (force-)pushes and retargets the PR, without adding code owners as reviewers in the process (suggested by raylu)
- improved: when running `git machete squash` against a root branch, the error message suggests using `--fork-point=...` flag (suggested by levinotik)
- improved: simplified & clarified docs in multiple places (partly suggested by kgadek)

- added: support for Python 3.12
- improved: `git machete github create-pr` also checks for `.github/pull_request_template.md` for description (contributed by raylu)