Add blog to docs (#484)

* Adding social card infrastructure
* Upgrades doc project to .NET 6
* Adds Playwright
* Changes the console to a web project for Playwright
* Adds social card template
* Added blog content
* Parallelized social image processing
* Updating CI to use .NET 6 for docs build

docs/input/appendix/borders.md

@@ -1,5 +1,11 @@
 Title: Borders
 Order: 2
+Description: "*Spectre.Console* makes it easy to create tables and panels with a variety of different styles of borders."
+Highlights:
+    - Rounded
+    - Square
+    - Heavy
+    - And more...
 ---
 
 There is different built-in borders you can use for tables and panels.

docs/input/appendix/colors.md

@@ -1,5 +1,9 @@
 Title: Colors
 Order: 0
+Description: "*Spectre.Console* allows easy rendering of the standard ANSI colors of your terminal, and also supports rendering up to 24-bit colors depending on the capabilities of your terminal."
+Highlights:
+    - Predefined common colors
+    - Easy syntax for inline styling
 ---
 
 The following is a list of the standard 8-bit colors supported in terminals.

docs/input/appendix/emojis.md

@@ -1,5 +1,9 @@
 Title: Emojis
 Order: 3
+Description: "For terminals that support Emojis, *Spectre.Console* supports a simple syntax for rendering emojis."
+Highlights:
+    - ":rocket: becomes 🚀"
+    - ":waning_gibbous_moon: becomes 🌖"
 ---
 
 Please note that what emojis that can be used is completely up to 

docs/input/appendix/spinners.md

@@ -1,5 +1,9 @@
 Title: Spinners
 Order: 4
+Description: "*Spectre.Console* supports over 80 different types of spinners, and allows new ones to be defined. They are used automatically with the controls"
+Highlights:
+    - Status display
+    - Progress display
 ---
 
 For all available spinners, see https://jsfiddle.net/sindresorhus/2eLtsbey/embedded/result/

docs/input/appendix/styles.md

@@ -1,5 +1,10 @@
 Title: Styles
 Order: 1
+Description: "*Spectre.Console* makes it easy to write text with different styles beyond colors. Depending on your terminal, it can make it easy to use styles such as"
+Highlights:
+    - Bold, Italic, Underline, strikethrough
+    - Dim, Invert
+    - Conceal, slowblink, rapidblink
 ---
 
 Note that what styles that can be used is defined by the system or your terminal software, and may not appear as they should.