Update Quick Pick API guide (#8074)

* Change mockups to screenshots

* Update headings

Author: ntrogh

api/ux-guidelines/images/examples/quick-pick-multi-select.png

@@ -32,29 +32,29 @@ MetaDescription: UX guidelines for quick picks used in a Visual Studio Code exte
 * Use a title when the placeholder can describe the purpose on its own
 * Use inputs without a placeholder
 
-## Multiple Steps
+## Multiple steps
 
 Quick Picks can be configured to feature multiple steps. Use these when you need to capture related-but-separate selections in a single flow. Avoid using quick picks for long flows with many steps—they aren't well suited to function as a wizard or similarly complex experience.
 
 ![Multi-step Quick Pick example](images/examples/quick-pick-multi-step.png)
 
-*Notes the "1/3" text in the Quick Pick title that indicates the current and total number of steps in the flow.*
+*Note the "1/3" text in the Quick Pick title that indicates the current and total number of steps in the flow.*
 
-## Multiple Selections
+## Multiple selections
 
 Use a multi-select quick pick for closely-related selections that need to be selected in one step.
 
 ![Multi-step Quick Pick example](images/examples/quick-pick-multi-select.png)
 
 ## Title
 
-Quick Picks can be also be configured to show a title bar above the main input and selection UI. Use a title when the user needs more context for the selection being made. Avoid using a title that uses a label already used in the Quick Pick's input placeholder.
+Quick Picks can also be configured to show a title bar above the main input and selection UI. Use a title when the user needs more context for the selection being made. Avoid using a title that uses a label already used in the Quick Pick's input placeholder.
 
 ![Multi-step Quick Pick example](images/examples/quick-pick-title.png)
 
-## Using Separators
+## Using separators
 
-Quick Pick Items can be grouped into clear sections using Quick Pick Separators. These feature a divider and label to clearly show the section. Use separators if the extension features a quick pick containing multiple obvious groups of selections.
+Quick Pick items can be grouped into clear sections using Quick Pick separators. These feature a divider and label to clearly show the section. Use separators if the extension features a quick pick containing multiple obvious groups of selections.
 
 ![Quick Pick with separators](images/examples/quick-pick-separators.png)