Improve XML character entities highlighting and comment

runtime/syntax/html.yaml

@@ -7,7 +7,7 @@ rules:
     - error: "<[^!].*?>"
     - symbol.tag: "(?i)<[/]?(a(bbr|cronym|ddress|pplet|rea|rticle|side|udio)?|b(ase(font)?|d(i|o)|ig|lockquote|r)?|ca(nvas|ption)|center|cite|co(de|l|lgroup)|d(ata(list)?|d|el|etails|fn|ialog|ir|l|t)|em(bed)?|fieldset|fig(caption|ure)|font|form|(i)?frame|frameset|h[1-6]|hr|i|img|in(put|s)|kbd|keygen|label|legend|li(nk)?|ma(in|p|rk)|menu(item)?|met(a|er)|nav|no(frames|script)|o(l|pt(group|ion)|utput)|p(aram|icture|re|rogress)?|q|r(p|t|uby)|s(trike)?|samp|se(ction|lect)|small|source|span|strong|su(b|p|mmary)|textarea|time|track|u(l)?|var|video|wbr)( .*|>)*?>"
     - symbol.tag.extended: "(?i)<[/]?(body|div|html|head(er)?|footer|title|table|t(body|d|h(ead)?|r|foot))( .*)*?>"
-    - special: "&[^;[[:space:]]]*;"
+    - special: "&(#[[:digit:]]{1,4}|#x[[:xdigit:]]{1,4}|[^[[:space:]]]+);"
     - symbol: "[:=]"
     - identifier: "(alt|bgcolor|height|href|id|label|longdesc|name|on(click|focus|load|mouseover)|size|span|src|target|type|value|width)="
     - constant.number: "(?i)#[0-9A-F]{6,6}"

runtime/syntax/xml.yaml

@@ -9,14 +9,9 @@ rules:
         start: "<!DOCTYPE"
         end: "[/]?>"
         rules: []
-    - comment:
-        start: "<!--"
-        end: "-->"
-        rules: []
-    - special:
-        start: "&"
-        end: ";"
-        rules: []
+    - comment: "<!--.+?-->"
+    # next line for highlighting of character entities doesn’t work as of now
+    - special: "&(#[[:digit:]]{1,4}|#x[[:xdigit:]]{1,4}|[^[[:space:]]]+);"
     - symbol.tag:
         start: "<\\??"
         end: "\\??>"