Add underlines to links in prose

[microbit-robert]

Bumps ui and ui-patterns to 0.2.0. The ui library includes a new
link recipe underlined by default with a standalone variation
which are used in this PR.

Visual changes (all were underline on hover to permanently underlined):

Documentation sidebar

• Reference section prose: all three link types from the Sanity content — external links, internal cross-references, and API links (DocumentationContent's link marks)
• API section: the description's "MicroPython" link at the top (ApiDocumentation), and any URLs inside docstrings (DocString — e.g. the music/speech/neopixel module docs)

Dialogs

• About dialog: contributors link, micropython.org link, the two GitHub source links, and the whole-sentence "story of MicroPython" link
• Welcome dialog: the guide link
• Post-save dialog: the "transfer hex" help link
• Not-found connect dialog: both checklist links and the standalone "troubleshoot" link
• Firmware-update dialog: the firmware guide link and its "troubleshoot" link

Editor and toasts (corrected)

• Module overlay (third-party module files): the "settings" link-button in the how-to sentence
• Project-load toast: the MakeCode link in the load-error message

Other changes, e.g., the use of the standalone variant are to preserve the current behaviour for standalone links not in prose.

[github-actions]

Preview build will be at
https://review-python-editor-v3.microbit.org/link-underlines/