[ admin ] update README-related instructions

Author: gallais

HACKING.md

@@ -244,23 +244,14 @@ you are never committing anything with a whitespace violation:
 Type-checking the README directory
 ----------------------------------
 
-* By default the README directory is not exported in the
-  `standard-library.agda-lib` file in order to avoid clashing with other people's
-  README files. This means that by default type-checking a file in the README
-  directory fails.
-
-* If you wish to type-check a README file, then you will need to change the line:
-  ```
-  include: src
-  ```
-  to
-  ```
-  include: src .
-  ```
-  in the `standard-library.agda-lib` file.
-
-* Please do not include this change in your pull request.
-
+* By default the README files are not exported in the
+  `standard-library.agda-lib` file in order to avoid
+  clashing with other people's README files.
+
+* If you wish to type-check a README file, then you will
+  need to change the present working directory to `doc/`
+  where an appropriate `standard-library-doc.agda-lib`
+  file is present.
 
 Continuous Integration (CI)
 ===========================