Document new minicon standard

[jimmynotjim]

Based on the rules identified in #547, document the standard for both editing and creating new icons.

[Dnpizarro]

@designlanguage I wanted to document the 40pt line width option. I'm thinking we should probably discuss over hang outs. I'll connect with you over chat.

[designlanguage]

@Dnpizarro - Yes, let's discuss over hangouts. From these screenshots, it looks like there might be a few exceptions. The arrow looks much thicker than 40 pt, and the $ looks thinner, so we should formalize if/where/when we use different rules. Same thing with filled in shapes like the fax machine.

It'll also be good to share with the team and get feedback on these. I'll add the initial explorations for documentation also:

Version	Samples
Original
Original w/ circle
30pt outline
30pt outline circle
30pt filled circle
40/30pt outline
50/30pt outline

[designlanguage]

Seeing the outlined version of the minicons in context, we wanted to try a more filled in version to help them stand out from the text.

We would still keep some elements outlined to help recognition (like paper).