Add DCO requirement

This commit also renames DOC.md to rustdoc.md
to prevent oopsies involving the newly-added DCO.txt.

DCO.txt

@@ -0,0 +1,34 @@
+Developer Certificate of Origin
+Version 1.1
+
+Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
+
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+
+
+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.

README.md

@@ -25,7 +25,7 @@ For example usage, see [the docs](https://docs.rs/ec4rs).
 
 The main repository for this library includes the EditorConfig
 [core tests](https://github.com/editorconfig/editorconfig-core-test)
-as a Git submodule. `ec4rs` should pass all of these tests.
+as a Git submodule. This library should pass all of these tests.
 To run the test suite, run the following commands in a POSIX-like shell:
 
 ```bash
@@ -34,3 +34,16 @@ git submodule update --init --recursive
 cmake -DEDITORCONFIG_CMD="$PWD/target/debug/ec4rs-parse" -Stests -Btests
 ctest --test-dir tests
 ```
+
+## License
+
+**ec4rs** is licensed under the
+[Apache License 2.0](https://www.apache.org/licenses/LICENSE-2.0.html)
+with no `NOTICE` text.
+
+Contributors submitting code changes must agree to the terms of the
+[Developer Certificate of Origin (DCO)](https://developercertificate.org/)
+to have their contributions accepted for inclusion.
+A copy of the DCO may be found in `DCO.txt`.
+Contributors should sign-off on their commits (see `git commit -s`)
+to indicate explicit agreement.

src/lib.rs

@@ -1,4 +1,4 @@
-#![doc = include_str!("../DOC.md")]
+#![doc = include_str!("../rustdoc.md")]
 #![deny(clippy::as_conversions)]
 #![deny(clippy::enum_glob_use)]
 #![deny(clippy::wildcard_imports)]