update README, add license

LICENSE

@@ -0,0 +1,7 @@
+Copyright 2024 Teemu Koivisto
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

@@ -9,3 +9,7 @@ You need NodeJS >=16 and pnpm >= 7.
 1. `pnpm i`
 2. `pnpm --filter types build`
 3. `pnpm client`
+
+## Contributing
+
+PRs and issues are more than welcome! I'd wish to add scales and chords and such but since I'm not that familiar with them, it would be nice if people could point out anything I got wrong. I intend to keep this app fairly simple and straighforward, just to satisfy my own needs. All code is open-source.