Add basic CSS caching to oranda

[jamesmunns]

This PR adds a very naive caching implementation when fetching the pre-built CSS. This applies only to assets that would be fetched over the network.

For larger workspace projects, the blocking requests can add a significant amount of time:

Before:

✓ >o_o< SUCCESS: Your site builds are located in `public`.
oranda build  1.03s user 0.30s system 10% cpu 12.634 total

After:

✓ >o_o< SUCCESS: Your site builds are located in `public`.
oranda build  0.85s user 0.22s system 28% cpu 3.740 total

In the future, it may be desirable to cache this at the filesystem level (in .cache/ or similar), or to handle this in a more common way, such as in a consistent manner managed by axoasset.

Debatable design decisions:

• Using a Vec instead of a HashMap:
  • This is pretty much just because Vec::new() is const and HashMap::new() isn't
  • I don't think we'll likely be troubled by O(n) vs O(1) lookup, particularly compared to a network request
• Using expect() on Mutex poisoning rather than bubbling up the error:
  • We literally do nothing but read and push with the mutex locked
  • If the mutex is poisoned something has gone horrifically wrong

Feel free to close this if y'all aren't interested, but 3-4 second iteration times for me is nicer than 12-15 second iteration times.

[Gankra]

This looks like a solid approach, but i'll give liv a chance to look at it since she was planning to do this next week

[jamesmunns]

Misc bonus I didn't realize while initially developing: This means that long running oranda dev builds only make a single network request. Verified with some extra tracing:

oranda dev
↪ >o_o< INFO: Found 88 paths to watch, starting watch...
↪ >o_o< INFO: Workspace detected, gathering info...
↪ >o_o< INFO: Building 29 workspace member(s)...
MnemosProjectOverview ↪ >o_o< INFO: Cache miss
MnemosProjectOverview ↪ >o_o< INFO: Building components: mdbook
         kernel ↪ >o_o< INFO: Used cache
            abi ↪ >o_o< INFO: Used cache
           mstd ↪ >o_o< INFO: Used cache
       spitebuf ↪ >o_o< INFO: Used cache
          alloc ↪ >o_o< INFO: Used cache
         forth3 ↪ >o_o< INFO: Used cache
   sermux-proto ↪ >o_o< INFO: Used cache
    trace-proto ↪ >o_o< INFO: Used cache
        crowtty ↪ >o_o< INFO: Used cache
     dumbloader ↪ >o_o< INFO: Used cache
         f3repl ↪ >o_o< INFO: Used cache
 allwinner-core ↪ >o_o< INFO: Used cache
          beepy ↪ >o_o< INFO: Used cache
      melpomene ↪ >o_o< INFO: Used cache
         mnemos ↪ >o_o< INFO: Used cache
         forth3 ↪ >o_o< INFO: Used cache
     mnemos-abi ↪ >o_o< INFO: Used cache
   mnemos-alloc ↪ >o_o< INFO: Used cache
mnemos-trace-proto ↪ >o_o< INFO: Used cache
   sermux-proto ↪ >o_o< INFO: Used cache
       spitebuf ↪ >o_o< INFO: Used cache
     mnemos-std ↪ >o_o< INFO: Used cache
        crowtty ↪ >o_o< INFO: Used cache
     dumbloader ↪ >o_o< INFO: Used cache
         f3repl ↪ >o_o< INFO: Used cache
 mnemos-d1-core ↪ >o_o< INFO: Used cache
   mnemos-beepy ↪ >o_o< INFO: Used cache
      melpomene ↪ >o_o< INFO: Used cache
↪ >o_o< INFO: Building workspace index page...
↪ >o_o< INFO: Used cache
✓ >o_o< SUCCESS: Your site builds are located in `public`.
✓ >o_o< SUCCESS: Your project is available at: http://127.0.0.1:7979
↪ >o_o< INFO: Path(s) ["/Users/james/personal/mnemos/oranda-workspace.json"] changed, rebuilding...
↪ >o_o< INFO: Workspace detected, gathering info...
↪ >o_o< INFO: Building 29 workspace member(s)...
MnemosProjectOverview ↪ >o_o< INFO: Used cache
MnemosProjectOverview ↪ >o_o< INFO: Building components: mdbook
         kernel ↪ >o_o< INFO: Used cache
            abi ↪ >o_o< INFO: Used cache
           mstd ↪ >o_o< INFO: Used cache
       spitebuf ↪ >o_o< INFO: Used cache
          alloc ↪ >o_o< INFO: Used cache
         forth3 ↪ >o_o< INFO: Used cache
   sermux-proto ↪ >o_o< INFO: Used cache
    trace-proto ↪ >o_o< INFO: Used cache
        crowtty ↪ >o_o< INFO: Used cache
     dumbloader ↪ >o_o< INFO: Used cache
         f3repl ↪ >o_o< INFO: Used cache
 allwinner-core ↪ >o_o< INFO: Used cache
          beepy ↪ >o_o< INFO: Used cache
      melpomene ↪ >o_o< INFO: Used cache
         mnemos ↪ >o_o< INFO: Used cache
         forth3 ↪ >o_o< INFO: Used cache
     mnemos-abi ↪ >o_o< INFO: Used cache
   mnemos-alloc ↪ >o_o< INFO: Used cache
mnemos-trace-proto ↪ >o_o< INFO: Used cache
   sermux-proto ↪ >o_o< INFO: Used cache
       spitebuf ↪ >o_o< INFO: Used cache
     mnemos-std ↪ >o_o< INFO: Used cache
        crowtty ↪ >o_o< INFO: Used cache
     dumbloader ↪ >o_o< INFO: Used cache
         f3repl ↪ >o_o< INFO: Used cache
 mnemos-d1-core ↪ >o_o< INFO: Used cache
   mnemos-beepy ↪ >o_o< INFO: Used cache
      melpomene ↪ >o_o< INFO: Used cache
↪ >o_o< INFO: Building workspace index page...
↪ >o_o< INFO: Used cache
✓ >o_o< SUCCESS: Your site builds are located in `public`.

[shadows-withal]

Thank you! This is a good start for sure