Updated contributing docs (#5028)

<!--- Provide a general summary of your changes in the Title above -->

## Description

<!--- Describe your changes in detail -->

<!--- Describe your changes in detail including motivation and any context -->

## Related Issue

<!--- This project only accepts pull requests related to open issues (GitIssues) -->

<!--- If suggesting a new feature or change, please discuss it in an issue first -->

<!--- If fixing a bug, there should be an issue describing it with steps to reproduce -->

<!--- Please link to the issue here: -->

## Motivation and Context

<!--- Why is this change required? What problem does it solve? -->

## How Has This Been Tested?

<!--- Please describe in detail how you tested your changes. -->

<!--- Include details of your testing environment, and the tests you ran to -->

<!--- see how your change affects other areas of the code, etc. -->

## Screenshots (if appropriate):

## How Has This Been Validated?

<!--- All changes need to be validated to confirm that they produce -->

<!--- scientifically accurate results. -->

<!--- If your changes include any new algorithms or changes to existing algorithms, -->

<!--- please indicate any publications or references for them. -->

<!--- If you manually validated the changes please indicate -->

<!--- what data you used and how you checked the results. -->

## Types of changes

<!--- What types of changes does your code introduce? Put an `x` in all the boxes that apply: -->

- [ ] New feature (non-breaking change which adds functionality)

- [ ] Documentation change (update to the documentation; no code change)

- [ ] Breaking change (fix or feature that would cause existing functionality to change)

- [ ] Infrastructure change (changes to things like CI or the build system that do not impact users)

## Checklist:

<!--- Go over all the following points, and put an `x` in all the boxes that apply. -->

<!--- - [ ] My code follows the code style of this project. -->

- [ ] I have read and agree to abide by the [Code of Conduct](https://github.com/USGS-Astrogeology/ISIS3/blob/dev/Code-Of-Conduct.md)

- [ ] I have read the [**CONTRIBUTING**](https://github.com/USGS-Astrogeology/ISIS3/blob/dev/CONTRIBUTING.md) document.

- [ ] My change requires a change to the documentation.

- [ ] I have updated the documentation accordingly.

- [ ] My change requires a change to the documentation and I have updated the documentation accordingly.

- [ ] I have added tests to cover my changes.

- [ ] All new and existing tests passed.

- [ ] I have added myself to the [.zenodo.json](https://github.com/USGS-Astrogeology/ISIS3/blob/dev/.zenodo.json) document.

- [ ] I have added any user impacting changes to the [CHANGELOG.md](https://github.com/USGS-Astrogeology/ISIS3/blob/dev/CHANGELOG.md) document.

When making a bug fix contribution, please add the [bug](https://github.com/USGS-Astrogeology/ISIS3/pulls?q=is%3Apr+label%3Abug+) label to your pull request. This will automatically cherry-pick your PR into the latest release branch so that it can be distributed in the next bug fix release.

When making a contribution for the first time, please add your name to the `.zenodo.json file.` We strongly recommend adding your affiliation and ORCiD to the `zenodo.json` file. These additions only have to happen once.

# Becoming a Committer

All contributors who land a non-trivial contribution should be on-boarded in a timely manner,

and added as a committer, and be given write access to the repository.

Committers are expected to follow this policy and continue to send pull requests, go through

proper review, and have other committers merge their pull requests.