Update installation docs (#1650)

Include CentOS 9 Stream and CentOS 8 Stream, in addition to updating the
openSUSE instructions to cover upstream vagrant package installation.

Closes: #1429
Closes: #1537

docs/assets/js/color_scheme.js

@@ -0,0 +1,63 @@
+function setTheme(theme) {
+    if (theme === "dark") {
+        jtd.setTheme('dark');
+        document.documentElement.setAttribute('data-theme', 'dark');
+        window.localStorage.setItem('theme', 'dark');
+    } else {
+        jtd.setTheme('light');
+        document.documentElement.setAttribute('data-theme', 'light');
+        window.localStorage.setItem('theme', 'light');
+    }
+}
+
+if (window.matchMedia) {
+    window.matchMedia('(prefers-color-scheme: dark)')
+        .addEventListener('change', event => {
+            if (event.matches) {
+                setTheme('dark');
+            } else {
+                setTheme('light');
+            }
+        });
+}
+
+function getUserThemePreference() {
+  return localStorage.getItem('theme') || getComputedStyle(document.documentElement).getPropertyValue('content') || 'system';
+}
+
+function saveUserThemePreference(preference) {
+  localStorage.setItem('theme', preference);
+}
+
+function getAppliedMode(preference) {
+  if (preference === 'dark') {
+    return 'dark';
+  }
+  if (preference === 'light') {
+    return 'light';
+  }
+  // system
+  if (matchMedia('(prefers-color-scheme: dark)').matches) {
+    return 'dark';
+  }
+  return 'light';
+}
+
+const colorScheme = document.querySelector('meta[name="color-scheme"]');
+function setAppliedMode(mode) {
+  setTheme(mode);
+}
+
+function modeSwitcher() {
+    let currentMode = document.documentElement.getAttribute('data-theme');
+    if (currentMode === "dark") {
+        setAppliedMode('light');
+        document.getElementById("theme-toggle").innerHTML = "Dark Mode";
+      } else {
+        setAppliedMode('dark');
+        document.getElementById("theme-toggle").innerHTML = "Light Mode";
+    }
+}
+
+let theme = getUserThemePreference();
+setAppliedMode(getAppliedMode(theme));