[material-ui][docs] Add Connect-related content

[danilo-leal]

• [x] I have followed (at least) the PR section of the contributing guide.

Work in progress — not ready for a review yet.

• https://deploy-preview-40848--material-ui.netlify.app/material-ui/getting-started/design-resources/#connect-figma-plug-in
• https://deploy-preview-40848--material-ui.netlify.app/material-ui/design-resources/mui-connect/

[mui-bot]

Netlify deploy preview

• docs/data/material/design-resources/connect/connect.md
• docs/data/material/design-resources/material-ui-for-figma/material-ui-for-figma.md
• docs/data/material/getting-started/design-resources/design-resources.md

Bundle size report

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[danilo-leal]

@samuelsycamore, we'll probably add more content soon, but I'd appreciate it if you could add a first pass to what we already have so far! :)