Replace emojis when NO_EMOJI env variable present

[matt-lebl]

When the NO_EMOJI environment variable is set, replace/eliminate emojis in output.

For instance, without NO_EMOJI set (normal behaviour):

With NO_EMOJI set:

Addresses #364.

[shadows-withal]

Out of curiosity, is there any prior work for this environment variable in other projects? Is there some sort of standard naming here that works with multiple CLI applications when you have it set?

[matt-lebl]

Unfortunately, not that I could find. I started with issue #364 and looked for an environment variable to suit it, eventually settling on NO_EMOJI after the similar NO_COLOR from https://no-color.org. There is however no precedent that I could find for NO_EMOJI in particular.

[shadows-withal]

@all-contributors please add @blerchy for code

[allcontributors]

@fmoko

I've put up a pull request to add @blerchy! 🎉