adds new-value to QSelect emits

[benkroeger]

this actually causes a warning in development mode. see vuejs/core#4803 for details

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Documentation
• Code style update
• Refactor
• Build-related changes
• Other, please describe: avoids warning when emitting custom event

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the dev branch (or v[X] branch)
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix: #xxx[,#xxx], where "xxx" is the issue number)
• It's been tested on a Cordova (iOS, Android) app
• It's been tested on a Electron app
• Any necessary documentation has been added or updated in the docs (for faster update click on "Suggest an edit on GitHub" at bottom of page) or explained in the PR's description.

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:
This is actually a cosmetic change - since the related fix have been proposed to vue as well. But i's nice to list custom events in a component's emits prop

[rstoenescu]

Hi,

Thanks for contributing, but this is a Vue bug and the correct way is to wait for it to be fixed rather than work around it from Quasar core.