Update Contribution Guidelines

[drey-bigney]

As maintainers of the OSMT project we want to update the contribution guidelines so that users wishing to contribute code to the project have a clearly outlined process to follow and understand the requirements that will lead to a successful contribution.

Suggested outline is as follows:
*Overview
*How to contribute

• Submit an Issue
• Submit a PR
• • Workflow
• • Style Guide
• • Commit message format
• • Tips
• Where to go for help

[drey-bigney]

WRT the Submit a PR section, based on the Technical Work Group discussion, we've arrived at the following decisions:

• We want to follow a branching workflow where committers create a branch containing the desired changes. This is the workflow that's been used to date by CSky.
• Target branch that changes should be based on is "develop".
• Branch name should be "feature/<feature_name>". where "feature_name" is a very brief description.
• Branches should be limited to a single feature, multiple unrelated features should handled by creating multiple branches vs batching changes in a single branch.
• Code will follow appropriate style guides (kotlin/angular)
• Unit tests are expected for new code