Create migration docs and deprecate package

[joshblack]

For our v10 release, we'll need to create a migration guide for @carbon/icons and officially deprecate this package.

Should we also include an FAQ for handling common questions for teams using this package?

[tay1orjones]

Is the intent to follow a similar deprecation strategy that security has implemented by modifying <Icon/> to accept icons from @carbon/icons-react instead of this library?

https://github.com/carbon-design-system/ibm-security/blob/dev/src/components/Icon/migrate-to-2.x.md

[joshblack]

@tay1orjones I think the hope will be to remove the usage of <Icon /> in preference of using the dedicated icons from the library.

I think there may be a use-case for us exporting the underlying <Icon /> component from the icons package itself, perhaps renamed to SVG, but the existing component will be removed.

Reference for the underlying Icon component from the new work: https://github.com/carbon-design-system/carbon/blob/master/packages/icon-build-helpers/src/builders/react/components/Icon.js

Let me know if you have any questions!