Serve: Launch different Zotero based on channel

[northword]

Launch different Zotero based on channel.

Also, in my practice I store the path to the beta channel in a user environment variable and expect to override the user-level environment variable via .env, but c12 does not yet support overriding env (see: unjs/c12#190); and modifying the env loaded by nodejs is relatively annoying.

Therefore, an option could be added to decide whether to read ZOTERO_PLUGIN_ZOTERO_BIN_PATH or ZOTERO_PLUGIN_ZOTERO_DEV_BIN_PATH. Of course, the variable names are just examples.