🔥 Remove $ from code fenced examples on readme

[phatblat]

GitHub adds a JavaScript "copy" button to these code fenced blocks which shows up on mouseover. When using this GH copy feature, these initial $s get included in the copied command forcing the user to delete the $ before running the command or else they get a shell error. Not a big deal, but removing these prompt symbols makes for a better first-time user experience.

Additionally, Markdownlint has a rule (MD014) where initial dollar signs should only be used when the code block is showing a command and the output, to help differentiate the two.