nit: Fix emojis in README

[bailey-coding]

What are you trying to accomplish with this PR?

The :eyes: and :runner: weren't rendering for me, for some strange reason.

How is this accomplished?

I tried doing some things with whitespace with no luck. Replacing them with the emojis worked, so then I changed the others too so they're consistent.

What could go wrong?

It's pretty low risk, because it's Markdown.