Deprecation Warnings from @material

[tuckergordon]

Describe the bug
Using themed components results in deprecation warnings from @Material (e.g. Using / for division is deprecated). This can be fixed by upgrading to the latest version of @Material (as of writing, that means upgrading from 11 to 12).

To Reproduce
Steps to reproduce the behavior:

1. Create a new Svelte project

npx degit sveltejs/template my-svelte-project`)

2. Install smui/button

npm install --save @smui/button

3. Go through the steps for the Advanced Styling Method
   a. npm install --save-dev sass rollup-plugin-postcss
   b. Add sass to your rollup config
   c. Add a blank _smui-theme.scss file (this prevents a compilation error, but it doesn't need any code in it)
4. Add a styled button to your App component:

<script>
  import Button from '@smui/button/styled';
</script>

<Button>Hello</Button>

5. npm run dev will result in deprecation warnings

Screenshots

Additional context

I've only tested this with Button, but manually installing the latest version of the material dependencies fixed the issue. E.g. installing

    "@material/button": "^12.0.0",
    "@material/elevation": "^12.0.0",
    "@material/feature-targeting": "^12.0.0",
    "@material/ripple": "^12.0.0",
    "@material/theme": "^12.0.0",

But given how many components there are, I wouldn't be surprised if others required more adjustments to work with the newer version of material.

[tuckergordon]

Also this is probably a separate issue, but I'm noticing slow build times with smui components. My guess is that it's related to the issues that Angular material also ran into - here and here

[Egnus]

This PR should help removing these warnings. Let's hope it works.

#350

[tuckergordon]

Whoops sorry, forgot to follow up. Yes, this was closed by #350