deps update for 2.5.0: (#542)

- bump to 2.5.0-rc.3
- update to electron 43 and wabac.js 2.27.0
- also update electron-updater

.gitignore

@@ -5,7 +5,7 @@
 *.warc.gz
 **/node_modules
 yarn-error.log
-/.yarn/install-state.gz
+.yarn/install-state.gz
 coverage/
 **/local-examples/
 **/.DS_Store
@@ -24,4 +24,4 @@ mkdocs/site/ruffle
 mkdocs/site/adblock
 ipfs-core.min.js
 _site
-test-results/
+test-results/