added contributing doc

Author: togglebyte

CONTRIBUTING.md

@@ -0,0 +1,13 @@
+# Contributing to the Anathema Guide
+
+Base your fork on the "dev" branch:
+```
+git clone https://github.com/togglebyte/anathema-guide
+git switch dev
+```
+
+Submit any PR to be merged back into the "dev" branch.
+
+## Getting help
+
+For help ask on [Discord](https://discord.gg/yZgdmXKf6p).

README.md

@@ -1,3 +1,7 @@
 # Anathema guide
 
 [The Guide](https://togglebyte.github.io/anathema-guide/) to using the Anathema TUI library.
+
+## Contributing
+
+See `CONTRIBUTING.md`