start documenting player prompt syntax

docs/guides/players.md

@@ -0,0 +1,25 @@
+# Player's Guide to TaleWeave AI
+
+## Contents
+
+- [Player's Guide to TaleWeave AI](#players-guide-to-taleweave-ai)
+  - [Contents](#contents)
+  - [Prompt Syntax](#prompt-syntax)
+    - [Prompt Function Syntax](#prompt-function-syntax)
+
+## Prompt Syntax
+
+### Prompt Function Syntax
+
+In order to call functions or use actions from your prompt replies, you (or more likely your GUI) can send valid JSON,
+or you can use this prompt function syntax.
+
+To use the prompt function syntax, start your prompt with `~` and use the syntax `~action:parameter=value,next=value`
+where `action` is the name of the action (the function being called) and the remainder are parameters to be passed into
+the function.
+
+There are some limits on this syntax:
+
+- the function name cannot contain `:`
+- the parameter names cannot contain `=`
+- the values cannot contain `,`