With this PR, when JS is activated and WASM supported, the article editor will be dynamically replaced with `contenteditable`s elements. This makes the editing interface simpler and less like a regular form. It will also allow us to easily add visual formatting with native browser APIs (and to insert images or videos directly). Here is a little demo:
There is still a lot to do, but it is a good first step.
Fixes#255
This change also remote all units for line-height to have more consistent styles and better cascading support. This solve the too small line height for multi line header in article and also add styling for h1 to h6 (previously h3 to h6 was not styled at all)
