Overhaul (#4)

**README**
- Overhaul; changed docs to be better aligned to the new `backup.sh`.
- Add example `docker-compose`.

**Dockerfile**
- Install `zip`.
- Remove installation of `sqlite`.
- Remove unnecessary variables.

**backup.sh**
- Overhaul; now zips all required and recommended files and directories stated at [vaultwarden docs](https://github.com/dani-garcia/vaultwarden/wiki/Backing-up-your-vault).
- Removed deleting old backups; will be added later on in a separate script.

**entrypoint.sh**
- Removed creating folders.

.github/workflows/lockdown.yml

@@ -1,34 +0,0 @@
-name: 'Lock down repository'
-
-on:
-  issues:
-    types: opened
-  pull_request:
-    types: opened
-
-jobs:
-  lockdown:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: dessant/repo-lockdown@v2
-        with:
-          github-token: ${{ github.token }}
-          issue-labels: 'off-topic'
-          issue-comment: >
-            Thanks for your contribution!
-            
-            However, this repository does not accept bug reports,
-            since this is only a mirror of
-            https://gitlab.com/1O/bitwarden_rs-backup.
-
-            Please feel free to open the issue there.
-          skip-closed-issue-comment: true
-          pr-comment: >
-            Thanks for your contribution!
-          
-            However, this repository does not accept pull requests,
-            since this is only a mirror of
-            https://gitlab.com/1O/bitwarden_rs-backup.
-
-            Please feel free to open the pull request there.
-          skip-closed-pr-comment: true