Move the reference documentation into the wiki, keep the README short (#61)

The twelve sections of the 992-line README are now wiki pages
(https://git.nockal.com/meleki/game-maker/wiki, wiki commit 9be1294),
content unchanged. The README keeps what it is, the quick start and
an index of the pages.

src/editor/shortcuts.ts

@@ -10,7 +10,7 @@ export interface ShortcutActions {
 }
 
 /**
- * Global keyboard shortcuts (see README "Keyboard"). Text fields keep their own key handling;
+ * Global keyboard shortcuts (see the wiki page "Keyboard"). Text fields keep their own key handling;
  * these only run when no focused widget consumed the key.
  */
 export function installShortcuts(state: EditorState, actions: ShortcutActions): void {