docs: Add RTD JS to integrate versions menu in the site navigation

Author: jodal

docs/javascript/readthedocs.js

@@ -0,0 +1,34 @@
+// Use CustomEvent to generate the version selector
+document.addEventListener("readthedocs-addons-data-ready", function (event) {
+  const config = event.detail.data();
+  const versioning = `
+<div class="md-version">
+<button class="md-version__current" aria-label="Select version">
+    ${config.versions.current.slug}
+</button>
+
+<ul class="md-version__list">
+${config.versions.active
+  .map(
+    (version) => `
+    <li class="md-version__item">
+    <a href="${version.urls.documentation}" class="md-version__link">
+        ${version.slug}
+    </a>
+            </li>`,
+  )
+  .join("\n")}
+</ul>
+</div>`;
+
+  // Check if we already added versions and remove them if so.
+  // This happens when using the "Instant loading" feature.
+  // See https://squidfunk.github.io/mkdocs-material/setup/setting-up-navigation/#instant-loading
+  const currentVersions = document.querySelector(".md-version");
+  if (currentVersions !== null) {
+    currentVersions.remove();
+  }
+  document
+    .querySelector(".md-header__topic")
+    .insertAdjacentHTML("beforeend", versioning);
+});

docs/overrides/main.html

@@ -0,0 +1,6 @@
+{% extends "base.html" %}
+
+{% block site_meta %}
+{{ super() }}
+<meta name="readthedocs-addons-api-version" content="1" />
+{% endblock %}