Update contributing guide to include precommit (#1044)

Author: cijothomas

.github/PULL_REQUEST_TEMPLATE.md

@@ -7,7 +7,7 @@ Please provide a brief description of the changes here.
 
 ## Merge requirement checklist
 
-* [ ] [CONTRIBUTING](../CONTRIBUTING.md) guidelines followed
+* [ ] [CONTRIBUTING](https://github.com/open-telemetry/opentelemetry-rust/blob/main/CONTRIBUTING.md) guidelines followed
 * [ ] Unit tests added/updated (if applicable)
 * [ ] Appropriate `CHANGELOG.md` files updated for non-trivial, user-facing changes
 * [ ] Changes in public API reviewed (if applicable)

CONTRIBUTING.md

@@ -58,6 +58,10 @@ Open a pull request against the main
 [opentelemetry-rust](https://github.com/open-telemetry/opentelemetry-rust)
 repo.
 
+> **Note**
+> It is recommended to run [pre-commit script](precommit.sh) from the root of
+the repo to catch any issues locally.
+
 ### How to Receive Comments
 
 * If the PR is not ready for review, please put `[WIP]` in the title,