mediawiki.ui: Reorder styleguide sections

Mostly to have checkboxes and radio buttons in neighboring sections.

Before:
  1. Inputs
  2. Buttons
  3. Forms
  4. Icons
  5. Checkbox
  6. Text & anchors
  7. Radio

After:
  1. Text inputs
  2. Buttons
  3. Checkbox
  4. Radio
  5. Forms
  6. Icons
  7. Text & anchors

Change-Id: I6b067eb90f5f05d7773c4879b87317436554701e
Merge "mediawiki.ui: Reorder styleguide sections"