Update filenames of JSON keymap exports (#1335)

Updates the filenames of JSON keymap exports to include the name of the
keyboard if the keymap name is given, instead of only the keymap name.

src/store/modules/app/getters.js

@@ -10,9 +10,11 @@ const getters = {
   filter: (state) => state.filter,
   exportKeymapName: (state) => {
     let exportName = state.keymapName.replace(/[\s/]/g, '_').toLowerCase();
+    let keyboardName = state.keyboard.replace(/[\s/]/g, '_').toLowerCase();
     if (exportName === '') {
-      let keyboardName = state.keyboard.replace(/[\s/]/g, '_').toLowerCase();
       exportName = `${keyboardName}_${state.layout}_mine`.toLowerCase();
+    } else {
+      exportName = `${keyboardName}_${exportName}`.toLowerCase();
     }
     // issue #331 whitelist what we send to API for keymapName and save to disk
     exportName = exportName.replace(/[^a-z0-9_-]/gi, '');