chore(repo): add addon-docs, remove addon-info and storybook-readme

[kevinsperrine]

Closes #963
Closes #2418

Blocked until #2359 and #2336 are merged.

Summary

• removes @storybook/addon-info
• removed storybook-readme
• replaces them with @storybook/addon-docs
• renames all existing MD files to MDX, and uses them as the basis for the new docs tab.
• sets a resolution for webpack 4, because of an incompatibility with an old webpack 4.28 version in the lockfile. 4.41 works fine.

Change List (commits, features, bugs, etc)
Component w/ stories using storybook-readme that were updated

• ListBuilder
• MapCard
• MenuButton
• MultSelect
• OverflowMenu
• Table

Acceptance Test (how to verify the PR)

• Clicking the new "Docs" tab (beside "Canvas" at the top left of the main storybook window) for any of the stories above should show their current docs
• The "Readme" tab should do longer appear

Regression Test (how to make sure this PR doesn't break old functionality)

• All stories should still function as expected

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[bjornalm]

Nice work, a small changes needed and there were some questions about dependencies

[bjornalm]

We have a problem with the new docs and modals:

[kevinsperrine]

We have a problem with the new docs and modals:

nice catch! I'll copy the MDX file from Carbon to prevent it and give better docs--this probably something we'll need to do eventually anyway, I assume. We were hoping carbon would bundle the MDX and we could just use then, but I don't know if that's going to happen or not.

[bjornalm]

We have a problem with the new docs and modals:
...
nice catch! I'll copy the MDX file from Carbon to prevent it and give better docs--this probably something we'll need to do eventually anyway, I assume. We were hoping carbon would bundle the MDX and we could just use then, but I don't know if that's going to happen or not.

It is not just the modal, but all stories that use the modal as well :-)

[bjornalm]

Nice work!