Git-machete

- fixed: wrong logo path in Snapcraft config

- added: `github` command with `anno-prs`, `checkout-prs`, `create-pr` and `retarget-pr` subcommands
- added: documentation on readthedocs.io
- fixed: documentation displayed with `help`/`-h`/`--help`
- improved: content of git-machete project related blogs has been moved to this repo and updated
- removed: releases to Nixpkgs no longer happen directly from our CI pipeline

- Fixed a race condition in the Slide-out action.
- Fixed a `NullPointerException` in Override Fork Point action.
- Improved Override Fork Point dialog: inapplicable options are hidden, placeholders are no longer displayed.
- Fixed an error with a too long GitHub URI when reporting exceptions in the plugin.
- Fixed a too short traverse info dialog.
- Improved Slide In dialog: clarified that a branch to slide in can be created on the spot

- improved: `show` can accept a target branch other than the current branch (contributed by asford)
- added: `--no-push`, `--no-push-remote`, `--push` and `--push-untracked` flags in `traverse` to optionally skip pushing to remote (contributed by asford)

- Improve CI build stability.
- Enhance the (Force) Push dialog with the default help action, the push tags option and the title indicating the repository.
- Improve the stability and reliability of the plugin.

- fixed: newly created branches were sometimes incorrectly recognized as merged to parent
- improved: GitHub API token is resolved from `gh` or `hub` if available