Custom HTML parser

[BjornDCode]

Currently we use rehype-perse which uses parse5 under the hood. It's a great parser but we are pushing it to the limits with some of the custom syntax in Stencil. Eventually we want to create a custom parser so we don't have to work around these limitations.

Here we can track all the things that depend on the custom HTML parser:

• Better @if directives #18
• Void components breaks elements after #30