[Docs] Update CONTRIBUTING.md

Author: PeterDaveHello

CONTRIBUTING.md

@@ -1,15 +1,20 @@
 Thanks for contributing to `nvm`!
 
-We love pull requests, they're our favorite.
+We love pull requests and issues, they're our favorite.
 
 However, before submitting, please review the following:
 
+For bug reports:
+ - Please make sure the bug is reproducible, and give us the steps to reproduce it, so that we can dig into the problem.
+ - Please give us as much detail as possible about your environment, so we can more easily confirm the problem.
+
+For pull requests:
  - Please include tests. Changes with tests will be merged very quickly.
  - Please manually confirm that your changes work in `bash`, `sh`/`dash`, `ksh`, and `zsh`. Fast tests do run in these shells, but it's nice to manually verify also.
  - Please maintain consistent whitespace - 2-space indentation, trailing newlines in all files, etc.
  - Any time you make a change to your PR, please rebase freshly on top of master. Nobody likes merge commits.
 
-Even if you don't have all of these items covered, please still feel free to submit a PR! Someone else may be inspired and volunteer to complete it for you.
+Even if you don't have all of these items covered, please still feel free to submit a PR/issue! Someone else may be inspired and volunteer to complete it for you.
 
 Thanks again!