On Debian, the `python3` command is the default one.

Aliases added:
- `assume`: ignore a file
- `assumed`: list ignored files
- `bclean`: clean up old branches
- `snapshot`: use snapshot stages
- `snapshots`: list snapshot stages
- `subup`: update all submodules
- `unassume`: unignore a file
- `upd`: update all git branches and clean up old ones.

New aliases: `la`, `alert` and `fromtimestamp`.

This variable lets highlight syntax in markdown.

This command formats JSON to be more readable.

The `plugged` directory is created by vim-plug.