Update links and tweak text on Embedded use case page

[kubamracek]

Fix a bunch of links to Embedded Swift docs:

• Point the main "Get Started" button to the getting started doc page.
• Link the pico guide to the correct new link.
• Put in the "learn more about platforms" link.
• Add more doc links in the bottom "Resources" section.
• Fix the LVGL demo link to the repo instead of the PR.

Also:

• Change "In just 788 bytes, Embedded Swift powers Conway’s Game of Life" into "In just 788 bytes of resulting compiled code..." because IMHO it's not clear that that the 788 bytes refer to the compiled result (it could be interpreted as source code having 788 bytes).

[shahmishal]

cc: @davelester for review