Move index.js to web_src and use webpack to pack them (#8598)

* Move index.js to web_src and use webpack

* Fix initHeatMap

* update eslint and move webpack to devDependencies

* update index.js

* add eslint env node

templates/repo/diff/comment_form.tmpl

@@ -39,7 +39,7 @@
 					{{end}}
 				{{end}}
 				{{if or (not $.HasComments) $.hidden}}
-					<button type="button" class="ui submit tiny basic button btn-cancel" onclick="cancelCodeComment(this);">{{$.root.i18n.Tr "cancel"}}</button>
+					<button type="button" class="ui submit tiny basic button btn-cancel" onclick="window.cancelCodeComment(this);">{{$.root.i18n.Tr "cancel"}}</button>
 				{{end}}
 			</div>
 		</div>