add a contributing guide

Signed-off-by: strawberry <strawberry@puppygock.gay>

docs/introduction.md

@@ -6,7 +6,7 @@
 
 #### What's different about your fork than upstream Conduit?
 
-See [differences.md](differences.md)
+See the [differences](differences.md) page
 
 #### How can I deploy my own?
 
@@ -14,4 +14,8 @@ See [differences.md](differences.md)
 
 If you want to connect an Appservice to Conduwuit, take a look at the [appservices documentation](appservices.md).
 
+#### How can I contribute?
+
+See the [contributor's guide](contributing.md)
+
 {{#include ../README.md:footer}}