docs: improves the Contribution guidelines (#3257)

Signed-off-by: Andres <[email protected]>
Co-authored-by: Andres <[email protected]>

CONTRIBUTING.md

@@ -1,41 +1,65 @@
-# Contributing to `cosign`
+# Contributing to Cosign
 
-The following document will detail the steps needed in order to ensure all of the correct processes are followed when contributing to `cosign`.
+Thank you for considering contributing to Cosign! We welcome any contributions, whether it's bug fixes, new features, or improvements to the existing codebase.
 
-The following are needed to be completed before a Pull Request is raised:
+## Your First Pull Request
 
-- unit tests written, run, and passing
-- lint run
-- document generation run
+Review [Sigstore's contribution guidelines](https://github.com/sigstore/community/blob/main/CONTRIBUTING.md) which includes some high level information on how to contribute to Sigstore projects.
 
-## Building
+To help you get familiar with our contribution process, we have a list of [good first issues](https://github.com/sigstore/cosign/issues?q=is%3Aissue+is%3Aopen+label%3A%22good+first+issue%22) which are relatively limited in scope.
 
-To build `cosign` locally, run the following:
+Before working on an issue, please:
+
+1. Check the comments to see if someone is already working on it.
+1. If it's unassigned, comment that you're working on it to avoid duplication.
+
+## Contribution Prerequisites
+
+Before running Cosign, ensure that you have [Go](https://go.dev/doc/install) installed.
+
+## Sending a Pull Request
+
+You can find a step by step guide to submit your contribution on [Sigstore's contribution guidelines](https://github.com/sigstore/community/blob/main/CONTRIBUTING.md#pull-request-process).
+
+The following steps describe the build, unit testing, linting, and documentation processes:
+
+### Building Cosign
+
+To build cosign locally, run this command:
 
 ```shell
 make cosign
 ```
 
-## Running Unit Tests
+### Running Unit Tests
 
-To run the unit tests, run the following:
+To run the unit tests, execute the following command:
 
 ```shell
 make test
 ```
 
-## Running Lint
+**Make sure all tests pass** without any failures or errors.
+
+### Running Lint
 
-To run linting, run the following:
+To run the linting checks, use the following command:
 
 ```shell
 make lint
 ```
+Address any linting warnings or errors before submitting your PR.
 
-## Document Generation
+### Document Generation
 
-To document generation, run the following:
+If your changes require updates to project documentation, run the following:
 
 ```shell
 make docgen
 ```
+
+Ensure that the documentation is up-to-date and reflects your changes accurately.
+
+### Sign DCO
+
+Make sure to sign the [Developer Certificate of Origin](https://git-scm.com/docs/git-commit#Documentation/git-commit.txt---signoff).