Work around mdbook-linkcheck2 bug.

It looks in the output.linkcheck section rather than its own.

Author: qwandor

book.toml

@@ -291,6 +291,15 @@ use-boolean-and = true
 [output.exerciser]
 output-directory = "comprehensive-rust-exercises"
 
+[output.linkcheck]
+optional = true
+follow-web-links = false # change to true to check web links
+exclude = [
+  "comprehensive-rust.pdf",
+  "comprehensive-rust-exercises.zip",
+  # "crates.io", # uncomment when follow-web-links is true
+]
+
 [output.linkcheck2]
 optional = true
 follow-web-links = false # change to true to check web links