Adds options for bar workspace button shape (#582)

* Add option for default workspace indicator radius

Enabling this option allows for the changing of the workspaces indicator
shape into a cornered rectangular/square shape.

This radius value was previously hard-coded for a full round indicator
shape. This change exposes an option in the `settings-dialog` under
Configuration > Bar > Workspaces > Indicator Radius

default value: `1.9rem * 0.6`

{
  "theme.bar.buttons.workspaces.radius": "1.9rem * 0.6"
}

* Adds options for workspace indicator height, width, and active_width

This adds some additional options to allow for further customization to
the default workspace indicators.

Nests the radius from my previous commit into an indicator scoped option:

```ts
theme: {
  bar: {
    workspaces: {
      indicator: {
        radius: opt('1.9rem * 0.6'),
        height: opt('4em'),
        width: opt('4em'),
        active_width: opt('12em'),
      }
    }
  }
}
```

* Apply suggestions from code review

---------

Co-authored-by: Jas Singh <jaskiratpal.singh@outlook.com>

src/options.ts

@@ -207,6 +207,12 @@ const options = mkOptions(CONFIG, {
                     numbered_active_underline_color: opt(colors.pink),
                     spacing: opt('0.5em'),
                     fontSize: opt('1.2em'),
+                    pill: {
+                        radius: opt('1.9rem * 0.6'),
+                        height: opt('4em'),
+                        width: opt('4em'),
+                        active_width: opt('12em'),
+                    },
                 },
                 windowtitle: {
                     background: opt(colors.base2),