Return AST rather than just an HTML string

[ignatiusmb]

Svelte now supports dynamic elements through https://svelte.dev/docs#template-syntax-svelte-element, it's time bump up the priority and implement individual token parsing and rendering.

[ignatiusmb]

Took a stab at this and foresaw a behemoth of a task waiting, let's do it on the next major.

[ignatiusmb]

With #103 and the addition of marker, users should be able to control what their content looks like on their own.