[LICENSE] Add hidden SPDX headers to markdown files

verilog/dv/README.md

diff --git a/verilog/dv/README.md b/verilog/dv/README.md
index 1c316a7..49cd280 100644
--- a/verilog/dv/README.md
+++ b/verilog/dv/README.md
@@ -1,3 +1,20 @@
+<!---
+# SPDX-FileCopyrightText: 2020 Efabless Corporation
+#
+# 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
+#
+#      http://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.
+#
+# SPDX-License-Identifier: Apache-2.0
+-->
 # DV Tests
 
 Organized into two subdirectories:

verilog/dv/caravel/mgmt_soc/gpio/README

diff --git a/verilog/dv/caravel/mgmt_soc/gpio/README b/verilog/dv/caravel/mgmt_soc/gpio/README
index f1935dd..baadc1f 100644
--- a/verilog/dv/caravel/mgmt_soc/gpio/README
+++ b/verilog/dv/caravel/mgmt_soc/gpio/README
@@ -1,3 +1,20 @@
+<!---
+# SPDX-FileCopyrightText: 2020 Efabless Corporation
+#
+# 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
+#
+#      http://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.
+#
+# SPDX-License-Identifier: Apache-2.0
+-->
 ------------------------------------------------
 Caravel
 gpio testbench

verilog/dv/caravel/user_proj_example/README.md

diff --git a/verilog/dv/caravel/user_proj_example/README.md b/verilog/dv/caravel/user_proj_example/README.md
index 244df05..503b8f4 100644
--- a/verilog/dv/caravel/user_proj_example/README.md
+++ b/verilog/dv/caravel/user_proj_example/README.md
@@ -1,3 +1,20 @@
+<!---
+# SPDX-FileCopyrightText: 2020 Efabless Corporation
+#
+# 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
+#
+#      http://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.
+#
+# SPDX-License-Identifier: Apache-2.0
+-->
 # Mega-Project Counter Tests
 
 The directory includes three tests for the counter mega-project example: 

verilog/rtl/README

diff --git a/verilog/rtl/README b/verilog/rtl/README
index bc1d751..f36a305 100644
--- a/verilog/rtl/README
+++ b/verilog/rtl/README
@@ -1,3 +1,21 @@
+<!---
+# SPDX-FileCopyrightText: 2020 Efabless Corporation
+#
+# 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
+#
+#      http://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.
+#
+# SPDX-License-Identifier: Apache-2.0
+-->
+
 A quick documentation of the Caravel memory map and operation
 ---------------------------------------------------------------