chore: point the placeholder homepage at the org wiki

The Cargo homepage feeds Plugin::URL, which hosts can show to users, so
the placeholder should be somewhere reachable rather than a github.com URL
that never existed.

This retires YOUR-USERNAME and YOUR-PLUGIN-NAME as canonical values, which
is the self-arming STALE mechanism working as designed: both were skipped
while they were part of HOMEPAGE and became live checks the moment they
were not. Both pass, since the whole URL was replaced.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WHt4DykxXaQnyaJfyS8KCn

README.md

@@ -75,10 +75,10 @@ after if you do.
 # No VST3 SDK needed — NIH-plug bundles its own bindings.
 
 # Build + bundle the CLAP (default)
-cargo xtask bundle nih_plug_template --release
+cargo xtask bundle plugin_name --release
 
 # Add the VST3 as well — see the licensing note below before you do this
-cargo xtask bundle nih_plug_template --release --features vst3
+cargo xtask bundle plugin_name --release --features vst3
 ```
 
 **Output:** `target/bundled/<name>.clap` (and `<name>.vst3` with `--features vst3`), where