Addon needs to be actualized to the last Storybook 6.2 Standards

[AkromeDev]

Hi, first thank you for making this addon and for taking the time to correct it! I found a few issues in the documentation of this addon.

1 - the demo link in the doc is broken (link to the doc below)
https://storybook.js.org/addons/storybook-addon-xd-designs

2 - Line:
""" Register the addon in addons.js
https://storybook.js.org/addons/storybook-addon-xd-designs/ """

This is false because:
Since storybook 5.3 3 "addon.js" has been replace with "manager.js" :

""" These files are now soft-deprecated, (they still work, but over time we will promote users to migrate):
• presets.js has been renamed to main.js. main.js is the main point of configuration for storybook.
• config.js has been renamed to preview.js. preview.js configures the "preview" iframe that renders your components.
• addons.js has been renamed to manager.js. manager.js configures Storybook's "manager" UI that wraps the preview, and also configures addons panel.

https://github.com/storybookjs/storybook/blob/master/MIGRATION.md#to-mainjs-configuration """

Having both "addon.js" and "manager.js" files causes this error:
2 - Line:
"
Register the addon in addons.js
https://storybook.js.org/addons/storybook-addon-xd-designs/
"
This is false because:
Since storybook 5.3 3 "addon.js" has been replace with "manager.js" :
"
These files are now soft-deprecated, (they still work, but over time we will promote users to migrate):
• presets.js has been renamed to main.js. main.js is the main point of configuration for storybook.
• config.js has been renamed to preview.js. preview.js configures the "preview" iframe that renders your components.
• addons.js has been renamed to manager.js. manager.js configures Storybook's "manager" UI that wraps the preview, and also configures addons panel.

Aus https://github.com/storybookjs/storybook/blob/master/MIGRATION.md#to-mainjs-configuration

"
Having both "addon.js" and "manager.js" files causes this error:

2 - Line:
"
Register the addon in addons.js
https://storybook.js.org/addons/storybook-addon-xd-designs/
"
This is false because:
Since storybook 5.3 3 "addon.js" has been replace with "manager.js" :
"
These files are now soft-deprecated, (they still work, but over time we will promote users to migrate):
• presets.js has been renamed to main.js. main.js is the main point of configuration for storybook.
• config.js has been renamed to preview.js. preview.js configures the "preview" iframe that renders your components.
• addons.js has been renamed to manager.js. manager.js configures Storybook's "manager" UI that wraps the preview, and also configures addons panel.

Aus https://github.com/storybookjs/storybook/blob/master/MIGRATION.md#to-mainjs-configuration

"
Having both "addon.js" and "manager.js" files causes this error:

3 - This link in the storybook is also broken:

it links to:

4 - this addon uses the function storiesOf:
""" Add your spec to the story!

https://storybook.js.org/addons/storybook-addon-xd-designs/ """

storiesOf is referenced as a legacy since Storybook 5.2. Here is the official documentation for "storiesOf":
https://github.com/storybookjs/storybook/blob/next/lib/core/docs/storiesOf.md

Thanks again for taking the time to correct these issues. Please contact me if you need more details.

[rajsite]

With npm 7 changes to peer dependencies normal npm installs in our storybook 6 project now fail because of the peerDependency conflict with storybook 5 used by this project.

Would appreciate a storybook 6 release so we can avoid using --legacy-peer-deps!