Improving pre-install content

Author: bobvan

browser.md

@@ -5,7 +5,8 @@ title: "Check Browser Requrements"
 Requiring a browser with Web Serial support avoids the need to
 install MCU downloading tools on your PC.
 
-Download a current version of Chrome or Edge.
-XXX add download links
+Download a current version of
+[Chrome](https://www.google.com/chrome/) or
+[Edge](https://www.microsoft.com/en-us/edge/download).
 
 Unfortunately, Safari and Firefox do not support Web Serial.

overview.md

@@ -3,6 +3,8 @@ title: "MicroPython Installation Overview"
 ---
 
 The order of these checks doesn't matter, but none are optional.
+An overview of the pre-install checklist follows.
+Click for details.
 
 ### Check [Browser](browser.html) Requirements
 

pc.md

@@ -4,5 +4,12 @@ title: "Check PC Requirements"
 
 You need a PC with a free USB port, either Type-A or Type-C.  
 
+| Type-A  | Type-C |
+| ------- | ------ |
+| [![USB Type-A Connector Photo](https://upload.wikimedia.org/wikipedia/commons/thumb/2/24/Blue_USB_port_without_USB_3.0_contacts.jpg/440px-Blue_USB_port_without_USB_3.0_contacts.jpg)](https://upload.wikimedia.org/wikipedia/commons/2/24/Blue_USB_port_without_USB_3.0_contacts.jpg) | [![USB Type-C Connector Photo](https://upload.wikimedia.org/wikipedia/commons/thumb/2/2d/MSI_Bravo_17_%280017FK-007%29-USB-C_port_PNr°0760.jpg/320px-MSI_Bravo_17_%280017FK-007%29-USB-C_port_PNr°0760.jpg)](https://upload.wikimedia.org/wikipedia/commons/2/2d/MSI_Bravo_17_%280017FK-007%29-USB-C_port_PNr°0760.jpg) |
+
 Your PC must run an OS supported by a browser that supports Web Serial.
+
 Unfortunately, that excludes Raspberry Pi.
+
+We know of no phones or tablets with browsers support Web Serial.