Add Clapper deamon subprocess

Daemon is responsible for starting and later watching over spawned "broadwayd" and "remote" app needed for remote playback control. We cannot use systemd n Flatpak, so we make do with running optional background subprocesses.

bin/com.github.rafostar.Clapper.Subprocess.in

@@ -0,0 +1,17 @@
+#!@GJS@
+
+/* pkg init enforces the imports path to the folder
+ * named after the pkg name, but I would prefer to have
+ * the bundled subprocess stored in the same directory */
+imports.searchPath.unshift('@datadir@/@PACKAGE_NAME@');
+
+const Package = imports.package;
+
+Package.init({
+  name: '@PACKAGE_NAME@.@ID_POSTFIX@',
+  version: '@PACKAGE_VERSION@',
+  prefix: '@prefix@',
+  libdir: '@libdir@',
+  datadir: '@datadir@',
+});
+Package.run(imports.clapper_src.main@ID_POSTFIX@);