📝 Initial repo contributors guide

.github/contributing.md

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+
+# 👩‍💻 Contributor's Guide
+
+## Software Development Lifecycle
+
+### Overview
+This project uses [Github Flow](https://docs.github.com/en/get-started/using-github/github-flow)
+for its software development lifecycle. Github workflow is a simple workflow 
+that works well for a small project with multiple developers needing to work 
+on the code and review each other's code before merging into the main branch.
+
+#### Process
+
+1. **Developer A** wants to make a change to the code
+2. On their local machine, developer A checkouts a branch to make that change
+3. **Developer B** wants to make a change to a different part of the code
+4. On their local machine, developer B checkouts a branch to make their change
+5. **Developer A** makes the change and pushes the code to the remote repo on Github
+6. **Developer A** opens a Pull Request (PR) so that others can review the change
+7. Other developers approve the Pull Request 
+8. **Developer A** squashes their branch's commits and merges the Pull Request into the main branch
+9. **Developer B** updates their local main branch with the changes that were just merged 
+10. **Developer B** squashes their branch's commits and merges the Pull Request into the main branch
+11. **Developer B** opens a Pull Request (PR) so that others can review the change
+12. Other developers approve the Pull Request 
+13. **Developer C** wants to make a release
+14. **Developer C** uses the [D3b Release Maker](https://github.com/d3b-center/d3b-release-maker) to 
+create a release PR on Github
+15. Other developers approve the Pull Request 
+16. **Developer C** merges the release PR which activates a Github workflow that tags the main branch with 
+the next version and creates the release on Github 
+
+
+Let's solidify this with an example.
+
+### Develop
+
+This assumes you've already setup your development environment. If not, 
+follow the steps in [Setup Dev Environment](#setup-dev-environment)
+
+#### Create a branch
+```shell
+# Checkout your local main branch
+git checkout main
+
+# Update your local main branch to mirror the main branch on Github
+git pull
+
+# Create a feature branch to work on. Name it something short and relevant 
+# to the change
+git checkout -b add-patient-birth-sex 
+```
+
+#### Make a change
+
+Commit messages
+
+#### ✅ Important - Rebase
+If another developer has merged their code (Pull Request) while you're working
+on your change, you will need to update your branch with those changes before
+you continue developing. To do that, you will need to [rebase your branch]()
+on the main branch like this:
+
+```shell
+# Checkout your local main branch
+git checkout main
+
+# Update your local main branch to mirror the main branch on Github
+git pull
+
+# Update your local branch with the changes on Github main branch 
+git checkout add-patient-birth-sex 
+git rebase main 
+
+# Push your updated branch to Github 
+git push -f
+```
+
+If you do this often you will rarely have conflicts.
+
+
+### Pull Request
+
+Once you're happy with your changes, its time to [open a Pull Request](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request?tool=webui)
+so that others can review your code and upon their approval you can merge your branch
+into the main branch.
+
+### Squash and Merge
+Once your PR has been approved you're ready to merge it. Before you merge it,
+you'll want to "squash" all of your commits into 1 commit. This cleans up your 
+branch's commit history and makes the main branch much cleaner as feature 
+branches are merged into it.
+
+This process is very easy to do because Github takes care of it for you. All you 
+need to do is select the the "Merge pull request" drop down menu on your 
+pull request page and press the button that says "Squash and merge".
+
+Here's an example of what happens with squashing:
+
+**Branch Commits Before Squashing**
+
+The git log for this branch shows 5 seperate commits
+
+```shell
+
+$ git log
+
+:sparkles: New birth sex field 
+
+:recycle: Change type 
+
+:recycle: Change values in ValueSet
+
+:bug: Fix typo in ValueSet
+
+:bug: Fix another typo in ValueSet
+```
+
+**Branch Commits After Squashing**
+
+Commits are combined into 1 new commit with a message that contains all
+individual commit messages to preserve history.
+
+```shell
+
+$ git log
+
+Merge pull request #19 from ncpi/add-patient-birth-sex
+:sparkles: New birth sex field 
+:recycle: Change type 
+:recycle: Change values in ValueSet
+:bug: Fix typo in ValueSet
+:bug: Fix another typo in ValueSet
+```
+
+
+
+### Release
+
+## TODO - Getting Started - Developers
+
+### Setup Dev Environment
+
+### Make a Change
+
+### Test
+
+### Push Code
+
+### Review
+
+
+