Add Usage Ping events for Static Site Editor

Contributes to https://gitlab.com/gitlab-org/gitlab/-/issues/233994

Add `merge_requests` and `commits` events

config/feature_flags/development/usage_data_static_site_editor_commits.yml

+---
+name: usage_data_static_site_editor_commits
+introduced_by_url:
+rollout_issue_url:
+milestone:
+type: development
+group: group::static_site_editor
+default_enabled: false

config/feature_flags/development/usage_data_static_site_editor_merge_requests.yml

+---
+name: usage_data_static_site_editor_merge_requests
+introduced_by_url:
+rollout_issue_url:
+milestone:
+type: development
+group: group::static_site_editor
+default_enabled: false

lib/gitlab/usage_data_counters/static_site_editor_counter.rb

@@ -3,7 +3,7 @@
 module Gitlab
   module UsageDataCounters
     class StaticSiteEditorCounter < BaseCounter
-      KNOWN_EVENTS = %w[views].freeze
+      KNOWN_EVENTS = %w[views commits merge_requests].freeze
       PREFIX = 'static_site_editor'
 
       class << self

spec/lib/gitlab/usage_data_counters/static_site_editor_counter_spec.rb

@@ -4,7 +4,11 @@ require 'spec_helper'
 
 RSpec.describe Gitlab::UsageDataCounters::StaticSiteEditorCounter do
   it_behaves_like 'a redis usage counter', 'StaticSiteEditor', :views
+  it_behaves_like 'a redis usage counter', 'StaticSiteEditor', :commits
+  it_behaves_like 'a redis usage counter', 'StaticSiteEditor', :merge_requests
 
   it_behaves_like 'a redis usage counter with totals', :static_site_editor,
-    views: 3
+    views: 3,
+    commits: 4,
+    merge_requests: 5
 end