Make thumbnail-url values null with a TBD comment

Author: dempseyatgithub

_data/go_further.yml

@@ -2,23 +2,23 @@
   description: "Swift has concurrency features built into the language making it easier to write concurrent code with the assistance of the compiler. This video introduces the async/await mechanism, a key part of Swift Concurrency."
   content-type: video
   content-url: https://developer.apple.com/videos/play/wwdc2021/10132/
-  thumbnail-url: TBD
+  thumbnail-url: #TBD
   release-date: 2021-06-08
 - title: "Go Further: Swift Generics"
   description: "In Swift, generics are a fundamental way to write abstract code. This video walks through the basics of Swift Generics and introducing generics into your code."
   content-type: video
   content-url: https://developer.apple.com/videos/play/wwdc2021/10132/
-  thumbnail-url: TBD
+  thumbnail-url: #TBD
   release-date: 2021-06-09
 - title: "Go Further: Regular Expressions"
   description: "Swift provides first-class regular expression support, commonly known as regex, for effective string processing. This video gives an overview of the power and flexibility of Swift Regex."
   content-type: video
   content-url: https://developer.apple.com/videos/play/wwdc2022/110357/
-  thumbnail-url: TBD
+  thumbnail-url: #TBD
   release-date: 2022-06-07
 - title: "Go Further: Swift Strings Under The Hood"
   description: "Swift strings provide a fast, Unicode-compliant way to work with text. In most cases"
   content-type: article
   content-url: https://www.swift.org/blog/utf8-string/
-  thumbnail-url: TBD
+  thumbnail-url: #TBD
   release-date: 2019-03-20