Switch from github emojis to standard emojis

[bmish]

Just use the standard ones for the fixable/recommended emojis.

Code editors like VSCode can't render :white_check_mark: but they can render standard emojis like ✅. Standard emojis are more universal and don't require special rendering engines. Easier to work with and preview locally.

[coveralls]

Coverage remained the same at 100.0% when pulling 927a7ea on bmish:docs-emojis into 742325c on platinumazure:master.

[platinumazure]

Changes generally look good, but I'll want to check how this looks in your branch when I'm on PC.

What's the motivation for this change? Does this solve a specific problem?

[bmish]

Code editors like VSCode can't render :white_check_mark: but they can render standard emojis like ✅. Standard emojis are more universal and don't require special rendering engines. Easier to work with and preview locally.