Update README.md to remove gitlab references

### Cloning and Rendering the Docs Locally

```bash

# 1. Clone the repository to your local machine:   

git clone git@code.usgs.gov:astrogeology/asc-public-docs.git

# 1. Create a fork of the repository (the fork button is on the upper right corner on GitHub)

# 2. Clone the repository to your local machine, replace <fork url> with your own fork.   

git clone <fork url>

cd asc-public-docs/

# 2. Create a branch to track your work

# 3. Create a branch to track your work

git checkout -b your-branch-name 

# 3. install dependencies 

# 4. install dependencies 

pip install -r requirements.txt

# 4. Make your changes to the code 

# 5. Make your changes to the code

# See "Adding Your Files" in the readme for details

# ...

# 5. Preview your changes, in the root of the repo run

# 6. Preview your changes, in the root of the repo run

mkdocs serve

```

# 6. Push your changes to the branch

To contribute changes back in: 

```bash

# 1. push changes back into your fork

git push origin your-branch-name

# Create a PR on this repository 

```

### Adding your files

### Adding Your Files

> See [mkdocs material docs](https://squidfunk.github.io/mkdocs-material/getting-started/) for information on how to work with mkdoc's material theme and it's features. 

1. The continuous deployment system should automatically deploy your new changes. 

1. Celebrate your contribution! :tada:

## Understanding The Doc System

Contributors should consider writing new docs under one of our four categories: