linkcheck: throw warnings instead of errors

Author: avivace

book.toml

@@ -43,6 +43,7 @@ site-url = "/pandocs/"
 follow-web-links = true
 traverse-parent-directories = false
 optional = true
+warning-policy = "warn"
 exclude = [
 	'https://github\.com/gbdev/pandocs/tree/', # Do not check the "this was generated from commit N" link, as the commit may not have been pushed yet
 	'print.html', # Do not check the print page, as it is generated separately