Naming and coding style convention, new linter tool. (#945)

* Makefile, Scripts: new linter
* About: remove ID from IC
* Firmware: remove double define for DIVC/DIVR
* Scripts: check folder names too. Docker: replace syntax check with make lint.
* Reformat Sources and Migrate to new file naming convention
* Docker: symlink clang-format-12 to clang-format
* Add coding style guide

applications/lfrfid/view/elements/button_element.h

@@ -0,0 +1,28 @@
+#pragma once
+#include "generic_element.h"
+
+typedef void (*ButtonElementCallback)(void* context);
+
+class ButtonElement : public GenericElement {
+public:
+    ButtonElement();
+    ~ButtonElement() final;
+    void draw(Canvas* canvas) final;
+    bool input(InputEvent* event) final;
+
+    enum class Type : uint8_t {
+        Left,
+        Center,
+        Right,
+    };
+
+    void set_type(Type type, const char* text);
+    void set_callback(void* context, ButtonElementCallback callback);
+
+private:
+    Type type = Type::Left;
+    const char* text = nullptr;
+
+    void* context = nullptr;
+    ButtonElementCallback callback = nullptr;
+};