chore(ui): Add comment for new theme spaces (#96003)

This PR adds in JSDoc comments for the new spaces values in the theme,
this makes it a bit easier to reference when using them, as I found
myself going back to a slack post to figure out which sizes lined up
with the previous space values.

---------

Co-authored-by: Nate Moore <[email protected]>
Co-authored-by: getsantry[bot] <66042841+getsantry[bot]@users.noreply.github.com>
Co-authored-by: Nate Moore <[email protected]>

Author: 3 people

static/app/utils/theme/theme.tsx

@@ -1092,13 +1092,37 @@ const iconSizes: Record<Size, string> = {
 
 const space = {
   none: '0px',
+  /**
+   * Equivalent to deprecated `space(0.25)`
+   */
   '2xs': '2px',
+  /**
+   * Equivalent to deprecated `space(0.5)`
+   */
   xs: '4px',
+  /**
+   * Equivalent to deprecated `space(0.75)`
+   */
   sm: '6px',
+  /**
+   * Equivalent to deprecated `space(1)`
+   */
   md: '8px',
+  /**
+   * Equivalent to deprecated `space(1.5)`
+   */
   lg: '12px',
+  /**
+   * Equivalent to deprecated `space(2)`
+   */
   xl: '16px',
+  /**
+   * Equivalent to deprecated `space(3)` (was `20px`)
+   */
   '2xl': '24px',
+  /**
+   * Equivalent to deprecated `space(4)` (was `30px`)
+   */
   '3xl': '32px',
 } as const;