Add GHA workflow for simulation of VHDL design

.github/workflows/test.yml

@@ -0,0 +1,11 @@
+name: 'tests'
+
+on: [ push, pull_request ]
+
+jobs:
+
+  test:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v1
+    - run: docker run --rm -tv $(pwd):/src -w /src/vhdl -e BUILD_NAME=ACCEPTANCE ghdl/vunit:llvm make sim

README.md

@@ -1,3 +1,5 @@
+[![tests](https://github.com/tmeissner/lfd111x_building_a_risc-v-cpu_core/workflows/tests/badge.svg?branch=master)](https://github.com/tmeissner/lfd111x_building_a_risc-v-cpu_core/actions?query=workflow%3Atests)
+
 The original repository is located on my own git-server at [https://git.goodcleanfun.de/tmeissner/lfd111x_building_a_risc-v-cpu_core](https://git.goodcleanfun.de/tmeissner/lfd111x_building_a_risc-v-cpu_core)
 
 It is mirrored to github with every push, so both should be in sync.