fix(vimdoc): adapt to breaking Neovim change

Problem:
cb46f6e467 (diff-edf997b0c2d42d31828800641ac1f5a46487fe24a0d46ccf70bcd58a14f3868f)
introduced a regression on how `#set!` behaves with several matches in a
single pattern, breaking conceals in, e.g., taglinks.

Solution: Separate taglink etc. patterns into concealed marker and
contents. Also add URL support for concealed markdown links.

queries/vimdoc/highlights.scm

@@ -12,12 +12,16 @@
 
 (tag
   "*" @label
-  (#set! conceal "")
+  (#set! conceal ""))
+
+(tag
   text: (_) @label)
 
 (taglink
   "|" @markup.link
-  (#set! conceal "")
+  (#set! conceal ""))
+
+(taglink
   text: (_) @markup.link)
 
 (optionlink
@@ -25,7 +29,9 @@
 
 (codespan
   "`" @markup.raw
-  (#set! conceal "")
+  (#set! conceal ""))
+
+(codespan
   text: (_) @markup.raw)
 
 ((codeblock) @markup.raw.block