add basic style guidelines

[valeriecollinsdesign]

Summary of changes

added basic style guidelines

Related Issue

#98

Changes include

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• [ x] Documentation (explains but does not affect functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)

Notes

• please consider including a gif that reflects your feelings about this PR

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[jischr]

Looks great- can you make sure there is no overlap with any of the other markdown files (contributing.md) I'm thinking of. You could also link this in the readme.