yarn doc tweaks

Author: Alain Dumesny

PULL_REQUEST_TEMPLATE.md

@@ -3,5 +3,5 @@ Please explain the changes you made here. Include an example of what your change
 
 ### Checklist
 - [ ] Created tests which fail without the change (if possible)
-- [ ] All tests passing (`npm test`)
+- [ ] All tests passing (`yarn test`)
 - [ ] Extended the README / documentation, if necessary

package.json

@@ -12,7 +12,7 @@
     "test": "grunt lint && karma start karma.conf.js",
     "lint": "grunt lint",
     "reset": "rm -rf dist node_modules",
-    "prepublishOnly": "npm build"
+    "prepublishOnly": "yarn build"
   },
   "keywords": [
     "gridstack",