[DOC] New doc about erb executable

[BurdetteLamar]

(Later) revision of README will briefly discuss the executable, then will link to this page.

(Later) revision of libexec/erb (the executable itself) will also link to this page.

[BurdetteLamar]

Converting to Draft; one more thing to do.

[k0kubun]

From the conversation at #76 (comment), my understanding was that #81 was going to be the last PR you will file at this time, but you've filed three more PRs.

Just curious, how many more documentations do you plan on contributing to in ERB? As I asked before, could you consider filing all ERB PRs you want at once, instead of filing one every day?

[BurdetteLamar]

From the conversation at #76 (comment), my understanding was that #81 was going to be the last PR you will file at this time, but you've filed three more PRs.

Just curious, how many more documentations do you plan on contributing to in ERB? As I asked before, could you consider filing all ERB PRs you want at once, instead of filing one every day?

I'll see what I can do.

[BurdetteLamar]

Closing this one; will re-open in larger PR.