Use new Retype features to update the theme and navigation

[geoffreymcgill]

New features

This pull request updates the retype.yml configuration file to enhance the docs.artblocks.io website appearance and functionality. The changes introduce a Pro mode for local development, a new navigation mode, and a customized theme with updated colors and styles.

Start in Pro mode

Adds a configuration to start Retype in pro mode when using retype start locally and does not require the Retype Pro key to installed locally.

start:
  # Start locally in Pro mode
  pro: true

Use the "Stack" navigation layout

Configure the left-sidebar navigation to use the new stack layout and hide the icons.

nav:
  mode: stack
  icons:
    mode: none

There are several different options for displaying the icons (or not), but we're turning them off for now which reduces the amount of thinking required to configure new content sections.

New theme colors

Customized a few of the new theme-variables (guide) to pick up some of the main artblocks.io website branding.

The colors for the base-color theme-variables were pulled from a Squiggle but can easily be customized to any value.

theme:
  base:
    base-color: "#9B19EF"
    base-bg: "#F9F9F9"
    base-text: "#1E1E1E"
    base-link-weight: 500
  dark:
    base-color: "#D41FD6"

All the latest features added to Retype are available in the Feature Log and release announcements.