docs(impl): write docs

doc/gopher.nvim.txt

@@ -11,6 +11,7 @@ Table of Contents
   Setup....................................................|gopher.nvim-setup|
   Install dependencies..............................|gopher.nvim-install-deps|
   Configuration...........................................|gopher.nvim-config|
+  Auto implementation of interface methods..................|gopher.nvim-impl|
 
 ------------------------------------------------------------------------------
                                                              *gopher.nvim-setup*
@@ -82,4 +83,35 @@ Parameters ~
 {user_config} `(optional)` gopher.Config
 
 
+==============================================================================
+------------------------------------------------------------------------------
+                                                              *gopher.nvim-impl*
+impl is utilizing the `impl` tool to generate method stubs for interfaces.
+Usage ~
+
+1. put your coursor on the struct on which you want implement the interface
+   and run `:GoImpl io.Reader`
+   which will automatically choose the reciver for the methods and
+   implement the `io.Reader` interface
+2. same as previous but with custom receiver, so put your coursor on the struct
+   run `:GoImpl w io.Writer`
+   where `w` is the receiver and `io.Writer` is the interface
+3. specift receiver, struct, and interface
+   there's no need to put your coursor on the struct if you specify all arguments
+   `:GoImpl r RequestReader io.Reader`
+   where `r` is the receiver, `RequestReader` is the struct and `io.Reader` is the interface
+
+simple example:
+>go
+   type BytesReader struct{}
+   //    ^ put your cursor here
+   // run `:GoImpl b io.Reader`
+
+   // this is what you will get
+   func (b *BytesReader) Read(p []byte) (n int, err error) {
+   	panic("not implemented") // TODO: Implement
+   }
+<
+
+
  vim:tw=78:ts=8:noet:ft=help:norl: