Add explicit ignore for more useless element

The tag names include: `<applet>`, `<element>`, `<isindex>`,
`<nextid>`, `<param>`, `<source>`, and `<track>`.

Author: wooorm

lib/handlers/index.js

@@ -33,6 +33,7 @@ exports.text = text
 exports.comment = comment
 exports.doctype = ignore
 
+exports.applet = ignore
 exports.area = ignore
 exports.basefont = ignore
 exports.bgsound = ignore
@@ -43,27 +44,33 @@ exports.command = ignore
 exports.content = ignore
 exports.datalist = ignore
 exports.dialog = ignore
+exports.element = ignore
 exports.embed = ignore
 exports.input = ignore
+exports.isindex = ignore
 exports.keygen = ignore
 exports.link = ignore
 exports.map = ignore
 exports.math = ignore
 exports.menu = ignore
 exports.menuitem = ignore
 exports.meta = ignore
+exports.nextid = ignore
 exports.noscript = ignore
 exports.object = ignore
 exports.optgroup = ignore
 exports.option = ignore
+exports.param = ignore
 exports.script = ignore
 exports.select = ignore
 exports.shadow = ignore
+exports.source = ignore
 exports.spacer = ignore
 exports.style = ignore
 exports.svg = ignore
 exports.template = ignore
 exports.title = ignore
+exports.track = ignore
 
 exports.abbr = all
 exports.acronym = all