Clarify argv and parse arguments

types/rc/index.d.ts

@@ -6,8 +6,16 @@
 declare function rc(
 	name: string,
 	defaults?: any,
+    /**
+     * Parsed argv object.  For example, if args were '--foo bar' then this value might be {foo: 'bar'}
+     * If null then rc's default argv parser will parse process.argv
+     */
 	argv?: {} | null,
+    /**
+     * Custom config file parser.
+      * Will be passed the string contents of each discovered config file and should return a parsed object dictionary.
+     */
 	parse?: ((content: string) => any) | null
 ): any;
 
-export = rc;
+export = rc;