Cleanup and improvements (#194)

- Lots of changes for migrating C code to C++
- Improved `Lockable` in several ways like adding `withLock()` (+ tests)
- Improved `Semaphore` a bit for improved readability, and also added some tests
- Upgrade Linux machine in GitHub Actions so that we can compile with a newer GCC
- Simplification of WiFi connection
- Updated funding options
- (and more)

Tactility/Source/app/AppManifest.h

@@ -61,10 +61,10 @@ typedef std::shared_ptr<App>(*CreateApp)();
 
 struct AppManifest {
     /** The identifier by which the app is launched by the system and other apps. */
-    std::string id;
+    std::string id = {};
 
     /** The user-readable name of the app. Used in UI. */
-    std::string name;
+    std::string name = {};
 
     /** Optional icon. */
     std::string icon = {};