Add a Nudge overview with some quick bullet points

Combined a couple of bullet points Erik wrote up on the MacAdmins Slack with my own bullet points. He also wanted me to include a link to my blog post for more details, so that's a last bullet point.

README.md

@@ -1,5 +1,12 @@
 # Nudge (macadmin's Slack #nudge)
 
+## Nudge functionality overview
+- Nudge, rather than trying to install updates, merely prompts users to install updates via an approved method (System Preferences, Munki, Jamf, etc.).
+- By default, Nudge will open every 30 minutes, at the 0 and 30 minute mark. This is because of the default launch agent. If you find this behavior too aggressive, please change the launch agent.
+- The timers are for if the user minimizes/hides the window. It will re-load the window into the foreground, taking precedence over any window.
+- If you want a certain number of days between notifications, you can set that using the `days_between_notifications` preference.
+- Read Alan Siu's [Introduction to Nudge](https://www.alansiu.net/2019/12/24/nudge/) blog post for a more in-depth introduction to Nudge.
+
 ## Embedded Python
 As of v2.0, Nudge now uses its own embedded python (currently v3.8). This is due to Apple's upcoming removal of Python2.