feat(jest): create jest config package for unit testing (#3678)

* feat(jest): create jest config package for unit testing
* chore: housekeeping
* fix: now we need to explicitly allow importing without extension
* fix: recover EditorDriverInterface import
* Apply suggestions from code review
* chore: yarn

Signed-off-by: Sami Mazouz <sychocouldy@gmail.com>

framework/core/js/webpack.config.cjs

@@ -0,0 +1,8 @@
+const config = require('flarum-webpack-config');
+const { merge } = require('webpack-merge');
+
+module.exports = merge(config(), {
+  output: {
+    library: 'flarum.core',
+  },
+});