add settings sidebar & initial templating support (#28)

packages/client/src/components/App.tsx

packages/client/src/components/CanvasWrapper.tsx

packages/client/src/components/Header.tsx

packages/client/src/components/Settings/SettingsSidebar.tsx

packages/client/src/components/Settings/TemplateSettings.tsx

packages/client/src/components/Template.scss

packages/client/src/components/Template.tsx

packages/client/src/contexts/AppContext.tsx

packages/client/src/contexts/TemplateContext.tsx

packages/client/src/lib/routes.ts

packages/client/src/lib/template.ts

packages/client/src/lib/webgl.ts

packages/client/src/style.scss

packages/lib/src/net.ts