Use all available space for HTML file editor

The HTML editor is used to edit documents that are usually larger than just a paragraph. Unlike a forum post or a description field it is a full document editor.

Currently the editor does not use the available space. Users have to resize the editor to fit the window. This issue is about improving the situation in a way that the manual resize is not necessary anymore.

The HTML editor shall be opened using all the available space and resize when the browser window is resized to match the window size.

See screenshots