Add REUSE

.github/workflows/reuse.yaml

@@ -0,0 +1,11 @@
+name: REUSE Compliance Check
+
+on: pull_request
+
+jobs:
+  test:
+  runs-on: ubuntu-latest
+  steps:
+    - uses: actions/checkout@v4
+    - name: REUSE Compliance Check
+      uses: fsfe/reuse-action@v4

README.md

@@ -1,6 +1,9 @@
 # ExSTARS
 
+[![hex](https://img.shields.io/hexpm/v/ex_stars.svg)](https://hex.pm/packages/ex_stars)
 [![CI](https://github.com/tombo-works/ex_stars/actions/workflows/ci.yaml/badge.svg)](https://github.com/tombo-works/ex_stars/actions/workflows/ci.yaml)
+[![license](https://img.shields.io/hexpm/l/ex_stars.svg)](https://github.com/tombo-works/ex_stars/blob/main/REUSE.toml)
+[![REUSE](https://api.reuse.software/badge/github.com/tombo-works/ex_stars)](https://api.reuse.software/info/github.com/tombo-works/ex_stars)
 
 Elixir STARS library.
 
@@ -27,3 +30,9 @@ Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_do
 and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
 be found at <https://hexdocs.pm/ex_stars>.
 
+## License
+
+This project is licensed under the Apache-2.0 license.
+
+And this project follows the REUSE compliance.
+For more details, see the [REUSE SOFTWARE](https://reuse.software/).

REUSE.toml

@@ -0,0 +1,20 @@
+version = 1
+
+[[annotations]]
+path = ["README.md", "lib/**", "mix.exs", "test/**"]
+SPDX-FileCopyrightText = "2024 Ryota Kinukawa"
+SPDX-License-Identifier = "Apache-2.0"
+
+[[annotations]]
+path = [
+  ".formatter.exs",
+  ".fwatch.exs",
+  ".fwatch.sh",
+  ".github/**",
+  ".gitignore",
+  ".tool-versions",
+  "REUSE.toml",
+  "mix.lock",
+]
+SPDX-FileCopyrightText = "2024 Ryota Kinukawa"
+SPDX-License-Identifier = "CC0-1.0"