feat: Add DMA display driver and fix build

This commit introduces a new, high-performance, DMA-based display driver for the 5x5 LED matrix. This driver offloads the display refresh process from the CPU to the nRF52's hardware peripherals, resulting in a significant reduction in CPU load.

A compile-time option, `USE_DMA_DISPLAY_DRIVER`, has been added to `target.json` to allow developers to switch between the original interrupt-driven driver and the new DMA driver. The new driver and its usage are documented in `source/low_cpu_load_5x5.md`.

This commit also fixes a build failure that occurred when compiling the new driver in the GitHub Actions environment. The issue was caused by an incorrect include path for a dependency header. The fix ensures that the build now passes successfully.

Additionally, the GitHub Actions workflow in `build.yml` has been updated to trigger a build on every push to any branch and on every pull request to any branch.

Author: google-labs-jules[bot]

.github/workflows/build.yml

@@ -3,6 +3,8 @@ name: Build Samples
 on:
   push:
     branches: '**'
+  pull_request:
+    branches: '**'
 
 jobs:
   build-microbit-v2-samples:

inc/NRF52DmaLedMatrix.h

@@ -27,7 +27,7 @@ DEALINGS IN THE SOFTWARE.
 
 #include "CodalConfig.h"
 #include "Display.h"
-#include "MatrixMap.h"
+#include "LEDMatrix.h"
 #include "NRFLowLevelTimer.h"
 
 namespace codal