Show battery percentage on home screen (#167)

## Summary

* Show battery percentage on home screen
  * Moved battery rendering logic into shared ScreenComponents class
* As discussed
https://github.com/daveallie/crosspoint-reader/discussions/155

src/activities/home/HomeActivity.cpp

@@ -6,6 +6,7 @@
 
 #include "CrossPointState.h"
 #include "MappedInputManager.h"
+#include "ScreenComponents.h"
 #include "fontIds.h"
 
 void HomeActivity::taskTrampoline(void* param) {
@@ -315,5 +316,7 @@ void HomeActivity::render() const {
   const auto labels = mappedInput.mapLabels("", "Confirm", "Up", "Down");
   renderer.drawButtonHints(UI_10_FONT_ID, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 
+  ScreenComponents::drawBattery(renderer, 20, pageHeight - 30);
+
   renderer.displayBuffer();
 }