Add a simple GitHub Action to check headers.

Signed-off-by: Tim 'mithro' Ansell <tansell@google.com>

.github/workflows/checks.yml

diff --git a/.github/workflows/checks.yml b/.github/workflows/checks.yml
new file mode 100644
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+++ b/.github/workflows/checks.yml
@@ -0,0 +1,36 @@
+# Copyright 2019-2021 SkyWater PDK Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# This code is *alternatively* available under a BSD-3-Clause license, see
+# details in the README.md at the top level and the license text at
+# https://github.com/google/skywater-pdk-libs-sky130_bag3_pr/blob/master/LICENSE.alternative
+#
+# SPDX-License-Identifier: BSD-3-Clause OR Apache 2.0
+
+
+name: Checks
+
+
+on:
+  push:
+  pull_request:
+
+
+jobs:
+  Run:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+
+    - uses: SymbiFlow/actions/checks@main