General improvements

[oh2fih]

• Update engines to match with the dependencies.
• Bugfix: make textarea non-resizable
• Update URLs to decrease HTTP redirections.
• Prettify some JSON files that had incoherent indentation.
• Add missing newlines at EOF of text files.

[oh2fih]

I find it a bit problematic that the inputHeaders textarea is resizeable while the position of the other elements is fixed.

This is easily fixable by making the textarea not resizeable; fixed in 1b62d6c.

[stephenegriffin]

Awesome work - thanks!