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)

TactilityHeadless/Source/hal/i2c/I2c.cpp

@@ -23,11 +23,12 @@ static Data dataArray[I2C_NUM_MAX];
 
 const char* initModeToString(InitMode mode) {
     switch (mode) {
-        case InitMode::ByTactility:
+        using enum InitMode;
+        case ByTactility:
             return TT_STRINGIFY(InitMode::ByTactility);
-        case InitMode::ByExternal:
+        case ByExternal:
             return TT_STRINGIFY(InitMode::ByExternal);
-        case InitMode::Disabled:
+        case Disabled:
             return TT_STRINGIFY(InitMode::Disabled);
     }
     tt_crash("not implemented");