…layout-config

* It is now possible to configure zellij through a layout:

  The config file and the layout file will be merged, on conflicting
  options the order is as follows:
  1. config options `zellij options`
  2. layout
  3. config

  Example:
```
---
template:
  direction: Horizontal
  parts:
    - direction: Vertical
      body: true
    - direction: Vertical
      borderless: true
      split_size:
        Fixed: 1
      run:
        plugin:
          location: "zellij:tab-bar"
default_shell: fish
```