ci(fpga): experimental FPGA bitstream action

For a future TT ASIC simulator board - see https://github.com/TinyTapeout/breakout-pcb/tree/main/ASIC-simulator/tt04-fpga-ICE40UP5k

.github/workflows/fpga.yaml

@@ -0,0 +1,17 @@
+name: fpga
+
+on:
+  push:
+  workflow_dispatch:
+
+jobs:
+  fpga:
+    runs-on: ubuntu-latest
+    steps:
+      - name: checkout repo
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: FPGA bitstream for TT ASIC Sim (ICE40UP5K)
+        uses: TinyTapeout/tt-gds-action/fpga/ice40up5k@fpga