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/blog/posts/_ViewStart.cshtml

@@ -0,0 +1,3 @@
+@{
+    Layout = @$"_layout.cshtml";
+}