Add README

README.md

@@ -0,0 +1,34 @@
+Advent of Code 2025 in R7RS-small Scheme
+
+# Implementations used
+
+- [Chibi](https://synthcode.com/scheme/chibi/)
+- [Chicken](https://call-cc.org)
+- [Gauche](https://practical-scheme.net/gauche/)
+- [Guile](https://www.gnu.org/software/guile/)
+- [Racket](https://github.com/lexi-lambda/racket-r7rs)
+- [Sagittarius](https://ktakashi.github.io/)
+- [Skint](https://github.com/false-schemers/skint) (excluded from some puzzles, as it lacks a numeric tower)
+
+# Testing
+
+Requires [BSD make](https://crufty.net/help/sjg/bmake.html).
+Targets:
+- `bmake`: test all implementations
+- `bmake <impl> ...`: test selected implementations
+- `bmake benchmark`: make a nice coloured benchmark table
+
+# License
+
+All code in this repository is licensed under the zero-clause BSD license included below. It's probably terrible code anyway
+
+Permission to use, copy, modify, and/or distribute this software for
+any purpose with or without fee is hereby granted.
+
+THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL
+WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
+OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE
+FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY
+DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
+AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
+OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.