Multiple new settings, app components import, multiple format exports, static folder, ...

[fdoflorenzano]

This PR adds a bunch of options that enable more personalization apart from custom imports:

Added

• Support to import custom SideBar React component that replaces sidebar in Mechanic UI. It's expected to be name-exported in in new app/ folder in mechanic project.
• New design function export ExtraUi, expected to be a React component that's added to the bottom section of sidebar, on top of default toggles and buttons.
• Support for SVG and PNG exports for SVG based engines like engine-react and engine-svg.
• New hideFeedback design function setting. When true, Mechanic's feedback button is hidden. Defaults to false.
• New hideNavigation design function setting. When true, the navigation input that let's users select a design function is hidden. Defaults to false.
• New hidePresets design function setting. When true, preset selection input is hidden. Defaults to false.
• New hideScaleToFit design function setting. When true, Scale to Fit toggle is hidden. Defaults to false.
• New scaleToFit design function setting. When false, Scale to Fit will be off initially. Defaults to true.
• New hideAutoRefresh design function setting. When true, Auto Refresh toggle is hidden. Defaults to false.
• New autoRefresh design function setting. When false, Auto Refresh will be off initially. Defaults to true.
• New hideGenerate design function setting. When true, Generate button is hidden. Defaults to false.
• New showMultipleExports design function setting. When false, single export button is shown. When true, two separate export buttons are shown: one for PNG export and another for SVG export. Defaults to false.
• New ignoreStyles design function setting. When true, CSS in iframe is injected into design function's SVG output. Defaults to false.
• Support to serve static/ folder for all design functions. Allows to serve custom favicon.
• _isPreview value is passed to design function handler in inputs argument. Allows design function to adjust if the render is a preview or an export.

[bravomartin]

Beautiful! Just some minor comments, mostly formal. Take any that make sense to you.

Approved! 🥇