fix(gatsby-theme-docz): make Props isToggle work again

[gogoyqj]

Description

fix #1323

Screenshots

Before	After

[Dangoo]

Checklist by @rakannimer:

• Add isToggle argument in Props definition : https://github.com/doczjs/docz/blob/master/core/gatsby-theme-docz/src/components/Props/index.js#L68
• Pass isToggle down to Prop https://github.com/doczjs/docz/blob/master/core/gatsby-theme-docz/src/components/Props/index.js#L74
• Add isToggle argument in Prop definition : https://github.com/doczjs/docz/blob/master/core/gatsby-theme-docz/src/components/Props/index.js#L23
• Initialize showing state to isToggle https://github.com/doczjs/docz/blob/master/core/gatsby-theme-docz/src/components/Props/index.js#L24

Syntactically looking good so far, thanks for your contribution!

[rakannimer]

Looks good 👍

[rakannimer]

Thanks @gogoyqj ! Will release an alpha and update here.

[rakannimer]

Will be released as 2.3.0. Currently released as 2.3.0-alpha.4. You can try it with : yarn add docz@next

[gogoyqj]

with pleasure