this adds a Cache-Control header to existing responses so they can be
cached in the browser. cache busting means this cache can be immutable
as if the file changes, the filename changes, so the browser will get
new files.
i abstraced the file handling out to a global static struct called
"Files" that is only written to once, in main inside a OnceLock. i also
split out asset handling into its own module folder called assets which
has all the asset handling code.
i also have a new crate called "proc_macros" which provides a attribute macro
that adds the base_template field to each struct i decorate with it
using the syn and quote crates.
the stylesheet got a new update from my websites stylesheet with the
bigger font sizes and i split the hyperlegible font face css into its
own file and made the asset code cleaner.
