This PR implements the Centered Layout feature (#4685):
- Added the `toggle centered layout` action.
- The centered layout mode only takes effect when there's a single
central pane.
- The state of the centered layout toggle is saved / restored between
Zed restarts.
- The paddings are controlled by the `centered_layout` setting:
```json
"centered_layout": {
"left_padding": 0.2,
"right_padding": 0.2
}
```
This allows us to support both the VSCode-style (equal paddings) and
IntelliJ-style (only left padding in Zen mode).
Release Notes:
- Added support for Centered Layout
([#4685](https://github.com/zed-industries/zed/pull/9754)).
https://github.com/zed-industries/zed/assets/2101250/2d5b2a16-c248-48b5-9e8c-6f1219619398
Related Issues:
- Part of #4382
Andrew Lygin
4eb1e65fbb