Allow users to toggle off the default style applied to their notes

[AustinFoss]

Is your feature request related to a problem? Please describe.

The problem is that the default CSS style that sets the H1 underline cannot be removed; at least from my own knowledge.

Describe the solution you'd like A button at the bottom of the editor that toggles whether or not style any of the MD file.

Describe alternatives you've considered

I've created the below document that does everything, I think*, that I want to achieve; an MD document with full control of the document's styles such as the border-bottom in the H1 and fonts. Plus the defaults automatically bold the H1, and may have other defaults I'd like to wipe clean.

<style>

    h1 {border-bottom: none !important;}
    #md-document {all:initial;}

</style>

<div id="md-document">
    
# Some Title
**By: Austin Foss**
    
</div>

Because the all: initial; doesn't reset everything, and things like the h1's border-bottom need to individually be overridden I'd like a simpler way to not apply HackMD's default styles.

Additional context My solution doesn't override the automatic bolding, I'm not sure how I would do that while still being able to use **<text>** to apply bolding.