Add repo badges to promote transparency and trust

[FYJen]

A few ideas:

• Security badge from https://snyk.io/
• Build passing badge
• Test cover badge
• NPM version badge

[EthanThatOneKid]

Here are some markdown links for some of the badge ideas you had, @FYJen.

NPM version badge:

CircleCI build passing badge:

Snyk.io security badge:

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This repository uses Ava for testing and there are not any test coverage badges that I can find on shields.io.