CLI: Add migrate command

[shilman]

Issue: #1108

What I did

Add CLI migrate command:

Usage: migrate [options] [migration]

Run a storybook codemod migration on your source files

Options:
  -l --list         List available migrations
  -g --glob <glob>  Glob for files upon which to apply the migration (default: "**/*.js")
  -n --dry-run      Dry run: verify the migration exists and show the files to which it will be applied
  -h, --help        output usage information

How to test

./lib/cli/bin/index.js migrate --list"
./lib/cli/bin/index.js migrate convert-to-module-format --glob "lib/ui/**/*.stories.js"

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[tmeasday]

Run a storybook code migration from an addon

But if I am reading this right it is just reading codemods from lib/codemod/src/transforms -- is that right?

I'm OK with that but the comment may have to change

[shilman]

@tmeasday Thanks! That was an old version. Updated the comment (the code was already updated).

[shilman]

Interpreting @tmeasday 's comment as an approval, since I'm blocked on this.