Ruflet Explorer v0.0.23

Resolve bundled package paths correctly on Windows

The Windows client build failed with every bundled package "missing": ruflet
must resolve to D:/a/.../ruflet_packages/ruflet, "got file://D/a/...".

package_config.json entries are resolved against a base URI built as
"file://" + the config path. A POSIX path starts with "/", so that yields the
three slashes a file URI needs. A Windows path starts with the drive, so
"file://D:/a/..." parses "D:" as the URI's host and drops it from the path --
which no local package could then match. URI#path also keeps the leading slash
on the way back, returning "/D:/a/..." to File.realpath.

Both directions now go through helpers that add the slash when the path does not
start with one and strip it back off ahead of a drive letter. POSIX paths are
untouched.