Move "Attach a file" option in markdown editor up into md-header-toolbar

Problem description

The standard markdown editor has the "Attach a file" option on the lower right. But all other options to interact with the content (the md-header-toolbar) are above the text content in the upper right. When I want to attach a file, I first look into this tool bar, sometimes clicking the "link" icon (because it kinda looks like a paper clip), then remember this option is not in the tool bar, before I find it in the lower right.

Proposal

• Move the action to "attach a file" up into the md-header-toolbar.
• Add paperclip button to toolbar
  • Tooltip: "Attach a file"

Current behaviour of the file dialog opening when the action is invoked is maintained.