Workspace lockfiles

Use `tmuxp freeze` to take exact layouts, current commands, etc. to save lockfiles

- `.config/`
  - `tmuxp/`
    - `locks/`
      - `global/`
        - `<workspace_name>/`
          - `<timestamp.yaml>`
      - `local/`
        - `<workspace_name>/`
          - `<timestamp.yaml>`