doc: split CONTRIBUTING.md

PR-URL: nodejs#18271
Fixes: nodejs#17842
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

.github/PULL_REQUEST_TEMPLATE.md

@@ -13,7 +13,7 @@ Contributors guide: https://github.com/nodejs/node/blob/master/CONTRIBUTING.md
 - [ ] `make -j4 test` (UNIX), or `vcbuild test` (Windows) passes
 - [ ] tests and/or benchmarks are included
 - [ ] documentation is changed or added
-- [ ] commit message follows [commit guidelines](https://github.com/nodejs/node/blob/master/CONTRIBUTING.md#commit-message-guidelines)
+- [ ] commit message follows [commit guidelines](https://github.com/nodejs/node/blob/master/doc/guides/contributing/pull-requests.md#commit-message-guidelines)
 
 ##### Affected core subsystem(s)
 <!-- Provide affected core subsystem(s) (like doc, cluster, crypto, etc). -->

COLLABORATOR_GUIDE.md

@@ -437,7 +437,7 @@ The TSC should serve as the final arbiter where required.
       author when squashing.
 
 Review the commit message to ensure that it adheres to the guidelines outlined
-in the [contributing](./CONTRIBUTING.md#commit-message-guidelines) guide.
+in the [contributing](./doc/guides/contributing/pull-requests.md#commit-message-guidelines) guide.
 
 Add all necessary [metadata](#metadata) to commit messages before landing.
 
@@ -467,7 +467,7 @@ $ git checkout master
 ```
 
 Update the tree (assumes your repo is set up as detailed in
-[CONTRIBUTING.md](CONTRIBUTING.md#step-1-fork)):
+[CONTRIBUTING.md](./doc/guides/contributing/pull-requests.md#step-1-fork)):
 
 ```text
 $ git fetch upstream
@@ -562,7 +562,7 @@ commit logs, ensure that they are properly formatted, and add
 `Reviewed-By` lines.
 
 * The commit message text must conform to the
-[commit message guidelines](./CONTRIBUTING.md#commit-message-guidelines).
+[commit message guidelines](./doc/guides/contributing/pull-requests.md#commit-message-guidelines).
 
 <a name="metadata"></a>
 * Modify the original commit message to include additional metadata regarding