feat(build): a bundled Credits.html feeds the macOS About panel - #37

…in#8)

AppKit shows Resources/Credits.html in the standard About panel only
when the options dictionary carries no Credits key — and the launcher
always passed one ("Made with tinyjs"), shadowing the macOS convention
for every app. When the project ships a Credits.html, the build now
copies it to Resources/ and the launcher omits the hardcoded key, so
the default macOS behavior takes over; without one, nothing changes
(the tinyjs credit stays).

Requested in tarwin#8 (Credits.html + Resources-root files were the one case
the sidecar discussion surfaced that needed no new API — convention
over configuration). Reported as a working hack by @Blatman via a
rebuilt launcher; this lands it properly.

Verified: launcher compiles; a project with Credits.html builds with
the file in Contents/Resources/ and passes codesign --verify --strict;
a project without builds exactly as before. The About panel's visual
behavior follows documented AppKit semantics (no Credits key →
Credits.html) — same result @Blatman confirmed with his rebuild.

tarwin#8 review: the tinyjs credit line was hardcoded, which blocks
white-labeled apps that don't ship a Credits.html. The manifest
"attribution" string (dev via TINYJS_ATTRIBUTION env, packaged via the
TinyjsAttribution plist key, the same dual path as TinyjsUserAgent)
replaces it. Precedence: bundled Credits.html → attribution → the
tinyjs default; existing apps change nothing.

README documents the chain in the About section.