Implement code frequency graph (#29191)

### Overview
This is the implementation of Code Frequency page. This feature was
mentioned on these issues: #18262, #7392.


It adds another tab to Activity page called Code Frequency. Code
Frequency tab shows additions and deletions over time since the
repository existed.


Before:
<img width="1296" alt="image"
src="https://github.com/go-gitea/gitea/assets/32161460/2603504f-aee7-4929-a8c4-fb3412a7a0f6">

After:
<img width="1296" alt="image"
src="https://github.com/go-gitea/gitea/assets/32161460/58c03721-729f-4536-a663-9f337f240963">

---


#### Features
- See additions deletions over time since repository existed
- Click on "Additions" or "Deletions" legend to show only one type of
contribution
- Use the same cache from Contributors page so that the loading of data
will be fast once it is cached by visiting either one of the pages

---------

Co-authored-by: Giteabot <teabot@gitea.io>

web_src/js/features/code-frequency.js

@@ -0,0 +1,21 @@
+import {createApp} from 'vue';
+
+export async function initRepoCodeFrequency() {
+  const el = document.getElementById('repo-code-frequency-chart');
+  if (!el) return;
+
+  const {default: RepoCodeFrequency} = await import(/* webpackChunkName: "code-frequency-graph" */'../components/RepoCodeFrequency.vue');
+  try {
+    const View = createApp(RepoCodeFrequency, {
+      locale: {
+        loadingTitle: el.getAttribute('data-locale-loading-title'),
+        loadingTitleFailed: el.getAttribute('data-locale-loading-title-failed'),
+        loadingInfo: el.getAttribute('data-locale-loading-info'),
+      }
+    });
+    View.mount(el);
+  } catch (err) {
+    console.error('RepoCodeFrequency failed to load', err);
+    el.textContent = el.getAttribute('data-locale-component-failed-to-load');
+  }
+}