Tabs and spaces are mixed when `use-tabs: true`

Hi, first of all thank you for the lib 👍

Issue

When I configured prettyhtml to useTabs it indents using tabs except for the HTML attributes. Attributes indented using spaces. Which I guess should be indented using tabs. See the example below.

Example

Ascii chars:

·  Represents a space char

→  Represents a tab char

Options:

{
  useTabs: true,
  tabWidth: 2,
  printWidth: 80
}

Input:

<div class="test">
··<prism-editor
····class="my-editor"
····:code="code"
····@change="changeCode"
····language="html"
··/>
</div>

Expected Output:

<div class="test">
→   <prism-editor
→   →   class="my-editor"
→   →   :code="code"
→   →   @change="changeCode"
→   →   language="html"
→   />
</div>

Got:

<div class="test">
→   <prism-editor
→   ··class="my-editor"
→   ··:code="code"
→   ··@change="changeCode"
→   ··language="html"
→   />
</div>

you can also test it on prettyhtml.netlify.com

• Click VUE example button
• Click the Use Tabs option on the left
• Click Run button on the top right

You should see that attributes are indented using spaces not with tabs.

[StarpTech]

The fix was released with prettyhtml@0.1.7

[koca]

🎉 🎉 😄