Add blush as the opposite of hush

[i-am-the-slime]

Description of the change

Adds a method blush that turns Eithers into Maybes of their possible Left values.
Often, I only care about Errors (e.g. when I have an Either Err Unit) and this function would come in handy.
Feel free to close this if you think it's a bad idea.

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Checklist:

• Added the change to the changelog's "Unreleased" section with a reference to this PR (e.g. "- Made a change (#0000)")
• Linked any existing issues or proposals that this pull request should close
• Updated or added relevant documentation
• Added a test for the contribution (if applicable)

[JordanMartinez]

I think this should be added. I like the name as well.

[JordanMartinez]

@garyb Can you approve this, so we can merge it?