feat: group membership requests (#2516)

* added event for group membership request

* small update to improve the performance of findImpl fix

* window.compareWwebVersions fixed

* added getGroupMembershipRequests method

* added approveGroupMembershipRequest method

* correct module for getGroupMembershipRequests

* membershipRequestAction separated to Injected.js

* docs clarification for approveGroupMembershipRequest

* added rejectGroupMembershipRequest method

* module fixed

* methods extension

* docs clarification

* force to update group membership requests

* docs fixed

* added usage example

* avoid sleep after the last iteration

* fix: added missing modules

* improve forcing to update group membership requests

* usage example clarification

* module refactored

* optional parameters

* usage example modified

* remove default values for membershipRequestAction

* added error description for memb req action

* usage example fixed

* return result even if ServerStatusCodeError

* default error message was missing

* removed line break

src/util/Constants.js

@@ -56,6 +56,7 @@ exports.Events = {
     GROUP_JOIN: 'group_join',
     GROUP_LEAVE: 'group_leave',
     GROUP_ADMIN_CHANGED: 'group_admin_changed',
+    GROUP_MEMBERSHIP_REQUEST: 'group_membership_request',
     GROUP_UPDATE: 'group_update',
     QR_RECEIVED: 'qr',
     LOADING_SCREEN: 'loading_screen',