fix: Check uploaded file size in widget and dashboard (#1975)

* File size check logic in widget

* set maxium file size

* update locale texts

* file size check in dashboard

* dynamincally set file size limit error message

* code climate review fixes

* add alert mixin

* move attahcment bus event to constants

* Move file size check logic to helper

* add specs for file size limit check helper

* changes as per review

app/javascript/shared/constants/messages.js

@@ -10,3 +10,5 @@ export const MESSAGE_TYPE = {
   ACTIVITY: 2,
   TEMPLATE: 3,
 };
+// Size in mega bytes
+export const MAXIMUM_FILE_UPLOAD_SIZE = 40;