Update docs to allow any file extension for rules.

It was already the case that there was no restriction on the extension
of rules files.  Just updating the docs to reflect that.

Author: bombaywalla

docs/configuration.md

@@ -86,7 +86,7 @@ Prompts can use variables like `$ARGS`, `$ARG1`, `ARG2`, to replace in the promp
 
     A `$XDG_CONFIG_HOME/eca/commands` or `~/.config/eca/commands` folder containing `.md` files with the custom command prompt.
 
-    `~/.config/eca/commands/check-performance.mdc`
+    `~/.config/eca/commands/check-performance.md`
     ```markdown
     Check for performance issues in $ARG1 and optimize if needed.
     ```
@@ -104,7 +104,8 @@ Prompts can use variables like `$ARGS`, `$ARG1`, `ARG2`, to replace in the promp
 ## Rules
 
 Rules are contexts that are passed to the LLM during a prompt and are useful to tune prompts or LLM behavior.
-Rules are Multi-Document context files (`.mdc`) and the following metadata is supported:
+Rules are text files (typically `.md` or `.mdc`, but any format works) with the following
+optional metadata:
 
 - `description`: a description used by LLM to decide whether to include this rule in context, absent means always include this rule.
 - `globs`: list of globs separated by `,`. When present the rule will be applied only when files mentioned matches those globs.
@@ -113,9 +114,9 @@ There are 3 possible ways to configure rules following this order of priority:
 
 === "Project file"
 
-    A `.eca/rules` folder from the workspace root containing `.mdc` files with the rules.
+    A `.eca/rules` folder from the workspace root containing `.md` files with the rules.
 
-    `.eca/rules/talk_funny.mdc`
+    `.eca/rules/talk_funny.md`
     ```markdown
     --- 
     description: Use when responding anything
@@ -126,7 +127,7 @@ There are 3 possible ways to configure rules following this order of priority:
 
 === "Global file"
 
-    A `$XDG_CONFIG_HOME/eca/rules` or `~/.config/eca/rules` folder containing `.mdc` files with the rules.
+    A `$XDG_CONFIG_HOME/eca/rules` or `~/.config/eca/rules` folder containing `.md` files with the rules.
 
     `~/.config/eca/rules/talk_funny.mdc`
     ```markdown
@@ -139,11 +140,11 @@ There are 3 possible ways to configure rules following this order of priority:
 
 === "Config"
 
-    Just add toyour config the `:rules` pointing to `.mdc` files that will be searched from the workspace root if not an absolute path:
+    Just add toyour config the `:rules` pointing to `.md` files that will be searched from the workspace root if not an absolute path:
 
     ```javascript
     {
-      "rules": [{"path": "my-rule.mdc"}]
+      "rules": [{"path": "my-rule.md"}]
     }
     ```