Andrew Overton f1d4dd25f0 [ProgressView] Add ProgressIndicators.md for material.io ...

The Material progress indicator component is broken down into two distinct iOS components, ProgressView and ActivityIndicator. This PR adds a new markdown file, `ProgressIndicators.md`, to be displayed for the progress indicator component on material.io, and leaves both the ProgressView and ActivityIndicator READMEs intact.

Preview the doc here: https://github.com/andrewoverton/material-components-ios/blob/material-io-progress-indicators/components/ProgressView/ProgressIndicators.md

Closes https://github.com/material-components/material-components-ios/pull/10136

COPYBARA_INTEGRATE_REVIEW=https://github.com/material-components/material-components-ios/pull/10136 from andrewoverton:material-io-progress-indicators 4daaa8cd80cd9bbf44c7d642324b591def841934
PiperOrigin-RevId: 345734425

2020-12-04 12:36:03 -08:00

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determinate-circular.png

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determinate-linear.png

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indeterminate-circular.gif

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indeterminate-linear.gif

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linear-progress-anatomy.png

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progress_view.png

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progress-indicator-hero.gif

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progress-indicator-types.gif

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shrine-linear-progress-indicator.gif

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