Quotes are added on empty known html arttributes

[StarpTech]

🐛 Bug Report

Omit quotes when possible. According to https://html.spec.whatwg.org/multipage/introduction.html#intro-early-example

Attributes are placed inside the start tag, and consist of a name and a value, separated by an "=" character. The attribute value can remain unquoted if it doesn't contain ASCII whitespace or any of " ' ` = < or >. Otherwise, it has to be quoted using either single or double quotes. The value, along with the "=" character, can be omitted altogether if the value is the empty string.

To Reproduce

Steps to reproduce the behavior:

When a known HTML attribute is used and it has no value we add quotes.

<v-layout row wrap>

result

<v-layout row wrap="">

Expected behavior

Quotes should only be added when the attribute has a value

Paste the results here:

<v-layout row wrap>

result

<v-layout row wrap>

Context

• Angular
• Svelte
• Vue
• Riot
• HTML5 only

Your Environment

• Prettyhtml version: 0.3.3