Add a quick start guide (#278)

* Add rough draft

* Rephrases

* Add link to quick start guide in README

* Update images to reflect main branch

* Update search url image and rephrase for clarity

* Add GitHub issue syntax docs link

Author: lauren-ciha

README.md

@@ -43,6 +43,10 @@ The Command Palette GitHub Extension is coming to the Microsoft Store. Stay tune
 
 For users who are unable to install the Command Palette GitHub Extension from the winget or the Microsoft Store, released builds can be manually downloaded from this repository's [Releases page](https://github.com/microsoft/CmdPalGitHubExtension/releases).
 
+## Using the extension
+
+Check out this [quick start guide](docs/quickstart.md) to get started.
+
 ---
 
 ## Contributing