Create new section in docs for Flutter concepts and add first article (#482)

* Create new section in docs for Flutter concepts and add first article

This article provides a comprehensive technical deep-dive into the Flutter SDK, covering its architecture, tooling, and update strategies. It discusses Dart's compilation methods, the Flutter engine's rendering pipeline, and introduces Shorebird for over-the-air updates.

* gertting things working

* remove md file

* get the video embed looking better

* spelling fixes

* update path

---------

Co-authored-by: Tom Arra <tarra3@gmail.com>

Author: dawn-ducky

.cspell.yaml

@@ -30,6 +30,7 @@ words:
   - elif
   - evenodd
   - ffigen
+  - jank
   - libapp
   - libflutter
   - libupdater
@@ -42,6 +43,8 @@ words:
   - podfile
   - prefs
   - previewable
+  - recompiles
+  - riverpod
   - rollouts
   - sdkman
   - shorebirdtech

astro.config.mjs

@@ -80,6 +80,11 @@ export default defineConfig({
           collapsed: true,
           autogenerate: { directory: 'system' },
         },
+        {
+          label: 'Flutter Concepts',
+          collapsed: true,
+          autogenerate: { directory: 'flutter-concepts' },
+        },
       ],
       plugins: [
         starlightAutoSidebar(),