fixes #305

fixes #257

- ESC closes the popup.
- Up/Down arrows for navigation.
- BackTab for backwards navigation.

fixes #301
fixes #302

Fixes #287

* Fix pop-up not showing when less than max 

* Select suggestion by pressing Enter

fixes #40

* Refactor widget items to use same interface

* Support audio, video, generic file for pasting

* Add utils function for human readable file sizes

* Set correct MIME type for media messages

This change also determines the size of the upload once from the
ContentLengthHeader, rather than seeking the QIODevice and asking for
its size. This prevents any future trouble in case the QIODevice is
sequential (cannot be seeked). The MIME type is also determined at
upload once, rather than using the QIODevice and the underlying data
inside.

* Allow for file urls to be used as fall-back

This fixes an issue on macOS which uses `text/uri-list` for copying
files to the clipboard.

fixes #228 

fixes #166

fixes #132 

fixes #24

fixes #134

The color scheme of nheko obeys the default color theme of Qt
(i.e. the system theme). It uses a Qt stylesheet to accomplish this,
which means replacing the color theme with a custom theme would only
be a matter of writing a new style sheet and loading it into the app.

This also fixes the transmission of mis-typed commands as messages,
fixes inability to send messages that start with a command, and does
some initial work towards automatically resizing the input field to fit
the input message.

fixes #116

- Ghetto disambiguation for the quick switcher
- Fix the Ctrl+K shortcut
- Fix keyboard focus when the quick switcher is closed

fixes #114

closes #41