Addon-docs/web-components: Add attributes to props table

[steel]

Issue:

The new web-components framework does not render attributes in the doc block.

What I did

I ran web-component-analyzer to get the most up to date custom-element.json file and added support for attributes when extracting props.

How to test

Here is what web components kitchen sink app now renders:

[vercel]

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🔍 Inspect: https://zeit.co/storybook/monorepo/mti5uur51
🌍 Preview: https://monorepo-git-fork-steel-web-component-attributes.storybook.now.sh

[daKmoR]

customElements.json was handwritten before 🙈 - for testing purposes 😅
awesome that auto-generation works that well 👍

let's make it fully nice then 💪

• remove set side and get side it's outdated code
• add a description to properties backSide, header, rows via the constructor like

/**
 * Indicates that the back of the card is shown
 */
this.backSide = false;

default is yet not supported by the analyzer but it's ok 😅

@runem be prepared for all the storybook users 💪 and yeah default and attribute on the properties would be nice 😬

[shilman]

This is pretty awesome guys 😻 - thanks @steel!!

[steel]

The buttons weren't clickable and the backside wasn't rendering properly for me in Safari. This fixes that.

[daKmoR]

thaankkk you 🤗

[steel]

@daKmoR I created a PR for default value runem/web-component-analyzer#117