[License] Add license header and contribution guide

1. add liencse header for all source code.
2. add contribution guide, which includes Developer Certificate of Origin.

Author: yaoyaoding

CONTRIBUTING.md

@@ -0,0 +1,62 @@
+# Tilus Contribution Guides
+
+## Signing your contribution
+To help ensure the integrity and authenticity of contributions, all contributors are required to sign their commits. This is done by adding a 'Signed-off-by' line to each commit message, certifying compliance with the Developer Certificate of Origin (DCO).
+
+### How to sign your commits
+
+You can sign your commits using the `-s` or `--signoff` option with `git commit`:
+
+```bash
+git commit -s -m "Your commit message"
+```
+
+This will append a line like the following to your commit message:
+
+    Signed-off-by: Your Name <[email protected]>
+
+Make sure the name and email address match your Git configuration. You can check your current settings with:
+
+```bash
+git config user.name
+git config user.email
+```
+
+If you need to update them:
+
+```bash
+git config --global user.name "Your Name"
+git config --global user.email "[email protected]"
+```
+
+All commits must be signed to be accepted.
+
+### Developer Certificate of Origin
+
+Developer's Certificate of Origin 1.1
+
+By making a contribution to this project, I certify that:
+
+(a) The contribution was created in whole or in part by me and I
+    have the right to submit it under the open source license
+    indicated in the file; or
+
+(b) The contribution is based upon previous work that, to the best
+    of my knowledge, is covered under an appropriate open source
+    license and I have the right under that license to submit that
+    work with modifications, whether created in whole or in part
+    by me, under the same open source license (unless I am
+    permitted to submit under a different license), as indicated
+    in the file; or
+
+(c) The contribution was provided directly to me by some other
+    person who certified (a), (b) or (c) and I have not modified
+    it.
+
+(d) I understand and agree that this project and the contribution
+    are public and that a record of the contribution (including all
+    personal information I submit with it, including my sign-off) is
+    maintained indefinitely and may be redistributed consistent with
+    this project or the open source license(s) involved.
+
+For more information, see https://developercertificate.org/.

examples/attention/flash_attention_v1.py

@@ -1,3 +1,5 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
 import numpy as np
 import pandas as pd
 import tilus

examples/attention/flash_attention_v2.py

@@ -1,3 +1,5 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
 import importlib.util
 
 import numpy as np

examples/attention/flash_attention_v3.py

@@ -1,3 +1,5 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
 import numpy as np
 import pandas as pd
 import tilus

examples/matmul/matmul_v0.py

@@ -1,3 +1,5 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
 """
 Naive Matmul
 ************

examples/matmul/matmul_v1.py

@@ -1,3 +1,5 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
 """
 Use Shared Memory
 =========================

examples/matmul/matmul_v2.py

@@ -1,3 +1,5 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
 """
 Auto-tuning
 ===========

examples/matmul/matmul_v3.py

@@ -1,3 +1,5 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
 """
 Use Async Copy
 ==============

examples/matmul/matmul_v4.py

@@ -1,3 +1,5 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
 """
 Software Pipelining
 ===================

examples/matmul/matmul_v5.py

@@ -1,3 +1,5 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
 """
 Split-K
 =======