Feature/resize panel

[murilopolese]

This PR does a little more than just resizing the panel.

• Loads Roboto Mono font locally
• Add smooth transition to buttons

Then it implements a panel resizing:

• The area that the terminal buttons reveal is not part of the resizable handle
• You can open and close the panel dragging
• If you click on close, it remember the last panel size so when you click open it goes back to that size
• If you move the mouse out of the window or into the tabs, resizing stops

[ubidefeo]

Maybe these 3 constants could indicate we're referring to HEIGHT.
Verbosity never hurts :)

[murilopolese]

It kind of does hurt, though. Of course the variable name can be PANEL_HEIGHT_CLOSED but I opted to keep the word height on the other side of the expression and leave the constant names shorter:

state.panelHeight = PANEL_CLOSED
state.savedPanelHeight = PANEL_DEFAULT

if (state.panelHeight < PANEL_TOO_SMALL) {
  ...
}

It also reads cleaner without the "height" on both sides, in my humble opinion.

[ubidefeo]

nice one