Improve READMEs

[GuillaumeDesforges]

Make READMEs

• more readable
• focus on what matters to get things started
• uniform across packages to facilitate navigation

[smelc]

LGTM :champagne: I would only swap the order of Run and Set up in a few places. Let me know how you wanna move forward @GuillaumeDesforges.

[GuillaumeDesforges]

@smelc thanks a lot! I'll go ahead and merge it. READMEs are easy to update and fix anyway :slightly_smiling_face: