Fix Contributing section in README.md

Before this change, the contributing section would define link with the syntax [text][id] and the id at the end of the file as reference. This doesn't seem to work (anymore?)

This change updates the section to use normal links [text](url) and mention opening a new discussion instead of only creating issues.

Author: szermatt

README.md

@@ -127,17 +127,16 @@ the following:
 
 ## CONTRIBUTING
 
-To report bugs, features or even to ask questions, please open an
-[issue][issues].  To contribute code or documentation, please open a
-[pull request][pull-requests].
+To report bugs, features, please open an [issue](
+https://github.com/szermatt/emacs-bash-completion/issues/new). To ask 
+questions or just for general comments, add a new [discussion](
+https://github.com/szermatt/emacs-bash-completion/discussions). To 
+contribute code or documentation, please open a [pull request](
+https://github.com/szermatt/emacs-bash-completion/pulls).
 
 See [CONTRIBUTING.md](CONTRIBUTING.md) for more details.
 
 ## COMPATIBILITY
 
 bash-completion.el is known to work with Bash 4.2 and later and Bash
 5, on Emacs, starting with version 25.3, under Linux and OSX.
-
-[new_issue]: https://github.com/szermatt/emacs-bash-completion/issues/new
-[issues]: https://github.com/szermatt/emacs-bash-completion/issues)
-[pull-requests]: (https://github.com/szermatt/emacs-bash-completion/pulls)