Added ci?

.github/workflows/ci.yml

@@ -0,0 +1,53 @@
+# Copied from https://github.com/tsoding/bm/blob/master/.github/workflows/ci.yml
+
+name: CI
+on: [push, pull_request]
+
+jobs:
+  build-linux-gcc:
+    runs-on: ubuntu-18.04
+    steps:
+      - uses: actions/checkout@v1
+      - name: build
+        run: |
+          $CC -o nob nob.c
+          ./nob init
+        env:
+          CC: gcc
+          CXX: g++
+  build-linux-clang:
+    runs-on: ubuntu-18.04
+    steps:
+      - uses: actions/checkout@v1
+      - name: build
+        run: |
+          $CC -o nob nob.c
+          ./nob init
+        env:
+          CC: clang
+          CXX: clang++
+  build-macos:
+    runs-on: macOS-latest
+    steps:
+      - uses: actions/checkout@v1
+      - name: build everything
+        run: |
+          $CC -o nob nob.c
+          ./nob init
+        env:
+          CC: clang
+          CXX: clang++
+  build-windows-msvc:
+    runs-on: windows-2019
+    steps:
+      - name: force LF
+        shell: cmd
+        run: |
+          git config --global core.autocrlf input
+      - uses: actions/checkout@v1
+      - uses: seanmiddleditch/gha-setup-vsdevenv@master
+      - name: build
+        shell: cmd
+        run: |
+          cl.exe nob.c
+          .\nob.exe init