Add another example for GHC-58481 (#575)

Author: Bodigrim

message-index/messages/GHC-39999/overloaded-number/index.md

@@ -19,7 +19,7 @@ Lib.hs:4:17: error: [GHC-39999]
 ## Explanation
 
 Sometimes, when GHC encounters a type error, it suggests solving
-it from an unexpected end. In this case, when it encouters a literal
+it from an unexpected end. In this case, when it encounters a literal
 instead of a list, it does not just complain about it. Instead it suspects
 that maybe an author meant to overload numeric literals so that they can mean lists too.
 

message-index/messages/GHC-58481/example6/after/CAPI.hs

@@ -0,0 +1,8 @@
+{-# LANGUAGE CApiFFI #-}
+
+module CAPI where
+
+import Foreign.C
+
+foreign import capi "setenv"
+  c_setenv :: CString -> CString -> CInt -> IO CInt

message-index/messages/GHC-58481/example6/before/CAPI.hs

@@ -0,0 +1,6 @@
+module CAPI where
+
+import Foreign.C
+
+foreign import capi "setenv"
+  c_setenv :: CString -> CString -> CInt -> IO CInt

message-index/messages/GHC-58481/example6/index.md

@@ -0,0 +1,13 @@
+---
+title: Use of `capi` calling convention
+---
+
+In this example the user attempted to use `capi` calling convention for foreign imports without enabling the `CApiFFI` extension, which leads to this generic parsing error.
+
+```
+CAPI.hs:5:16: error: [GHC-58481]
+    parse error on input ‘capi’
+  |
+5 | foreign import capi "setenv"
+  |                ^^^^
+```