OpenVK-KB-Heading: Editing notes

OpenVK wiki-markup is basically XHTML1.0 Transitional. The only difference is that we removed tags that are not needed or may harm OpenVK and it's users.
Allowed tags:
* All headers from level 3 to 6 (h3-h6)
* Paragraphs (<p>)
* Text formatting (<i>, <b>, <del>)
* <sup>, <sub>, <ins>
* Everything related to tables
* Links and images (<a>, <img>)
* Lists (и <ol> и <ul>)
* Line feed and horizontal rule (hr)
* Blockquotes (<blockquote> и <cite>)
* <acronym>

*Please note*: images can't have sourcemap and their source must be a file that is hosted on this OpenVK instance. This restrictions does not apply to links. Links can link to everything (except for data: and javascript: pseudoprotocols). They will be derefered though.
You may also have noticed, that <style> is note in the allowlist, however, we do support styling <div> and <img> tags using style attribute. This CSS properties are allowed:
* float
* height
* width
* max-height
* max-width
* font-weight
If property is a size property it can only accept pixels as value (no %, pt, pc, em, rem, vw or vh).