fix grammar in README.md

[brandondrew]

The apostrophe is for

• adding a possessive marker to a word: "This is John's car".
• contracting multiple words into one: "This isn't the way."

It's not needed for "gems", where the "s" marks plurality.

The hyphen is useful when two words form a single adjective, like in "This is a library-agnostic gem", where "library" internally modifies "agnostic" to change what sort of agnosticism the gem displays. If we used notation from LISP or math we might write "((library agnostic) gem)". But the case of "one specific icon" is different: it is one icon, and a specific icon—both "one" and "specific" are modifying "icon", so the hyphen doesn't belong.

I hope the explanations are helpful.

Thanks for the gem—it looks promising. ❤️

[eelcoj]

Thanks @brandondrew ❤️

[brandondrew]

you're very welcome!