Added transition mode default

[vHeemstra]

Description of Problem

According to the TypeScript interface (here) the default mode is default.

This was missing from the docs.

Proposed Solution

So I added it to this API docs page.

Additional Information

However, this might also be useful to mention in the guide where it introduces the mode parameter/attribute (VueJS.org / GitHub source). So developers know what to use for the default behaviour (if you have to set it explicitly).

It might seem obvious when you know the default value is default... but otherwise you might try an empty string, or 'sync' / false / null / etc.

[netlify]

✅ Deploy Preview for vuejs ready!

Name	Link
🔨 Latest commit	b32e28e
🔍 Latest deploy log	https://app.netlify.com/sites/vuejs/deploys/623ab28f3cd3960008687541
😎 Deploy Preview	https://deploy-preview-1632--vuejs.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site settings.

[skirtles-code]

Thanks for the addition.

Personally I think it's sufficient to include the value in just the API and not the guide. I don't think the need to set it explicitly to 'default' comes up often enough to justify covering it in the guide.