Rename COPYING to COPYING.txt

Signed-off-by: Eric Cornelissen <ericornelissen@gmail.com>

.editorconfig

@@ -8,7 +8,7 @@ insert_final_newline=true
 max_line_length=100
 trim_trailing_whitespace=true
 
-[{COPYING,DCO.txt}]
+[*.txt]
 indent_size=unset
 indent_style=space
 max_line_length=80

.gitignore

@@ -18,11 +18,13 @@
 
 # Docs
 !CONTRIBUTING.md
-!COPYING
-!DCO.txt
 !README.md
 !SECURITY.md
 
+# Legal
+!COPYING.txt
+!DCO.txt
+
 # Source
 !Makefile
 !go.mod

README.md

@@ -44,14 +44,14 @@ mitigation process.
 
 ## License
 
-The software is available under the `GPL-3.0-only` license, see [COPYING] for the full license text.
-The documentation is available under the `GFDL-1.3-or-later` license, see [GNU Free Documentation
-License v1.3] for the full license text.
+The software is available under the `GPL-3.0-only` license, see [COPYING.txt] for the full license
+text. The documentation is available under the `GFDL-1.3-or-later` license, see [GNU Free
+Documentation License v1.3] for the full license text.
 
 [`actions/github-script`]: https://github.com/actions/github-script
 [`run:`]: https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstepsrun
 [argus: a framework for staged static taint analysis of github workflows and actions]:https://www.usenix.org/conference/usenixsecurity23/presentation/muralee
 [blogged about this problem]: https://github.blog/2023-08-09-four-tips-to-keep-your-github-actions-workflows-secure/#1-dont-use-syntax-in-the-run-section-to-avoid-unexpected-substitution-behavior
-[copying]: ./COPYING
+[copying.txt]: ./COPYING.txt
 [gnu free documentation license v1.3]: https://www.gnu.org/licenses/fdl-1.3.en.html
 [workflow expression]: https://docs.github.com/en/actions/learn-github-actions/expressions