[docs][material-ui] Fix template shadow tokens

[zanivan]

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

Fixes item 24 from #41469

Based on #43369 from @Andarist, this PR fixes the shadows in the custom theme of the templates and adds the 23 remaining shadow tokens from the default theme.

[DiegoAndai]

Hey @zanivan! I think there's no need to copy the default shadows manually. Here's an example with a simplified version of the code: https://stackblitz.com/edit/stackblitz-starters-apzykp?file=src%2FApp.tsx

In themePrimitives.ts, the default theme is named customTheme:

material-ui/docs/data/material/getting-started/templates/shared-theme/themePrimitives.ts

Line 25 in 80237a4

const customTheme = createTheme();

Let's change it to defaultTheme.

[mui-bot]

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[DiegoAndai]

Should we look into sharing the TemplateFrame files as well? (having one source as we do with the themes)

[zanivan]

Should we look into sharing the TemplateFrame files as well? (having one source as we do with the themes)

This would be very helpful 🙏