Fix contributing link

[cmavr8]

Description

When opening a PR or issue, a link to the Contributing guidelines is provided. That link is broken. It is pointing to https://github.com/slackhq/goSDL/blob/master/.github/contributing.md instead of https://github.com/slackhq/goSDL/blob/master/CONTRIBUTING.md.

What type of issue is this? (place an x in one of the [ ])

• [ ] bug
• [ ] enhancement (feature request)
• [ ] question
• [x] documentation related
• [ ] testing related
• [ ] discussion

Requirements (place an x in each of the [ ])

• [x] I've read and understood the Contributing guidelines and have done my best effort to follow them.
• [x] I've read and agree to the Code of Conduct.
• [x] I've searched for any related issues and avoided creating a duplicate issue.

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Bug Report

Reproducible in:

{project_name} version: N/A

{platform_name} version: N/A

OS version(s): MacOS 10.15.7

Steps to reproduce:

1. Submit a PR
2. Click on the Contributing Guidelines link
3. Observe

Expected result:

Link works

Actual result:

Link doesn't work

Attachments: