Feat/menu select widget

[iam4x]

I'm opening this PR to keep track progress of the menuSelect widget.

• displays current refined value
• update results after new selected refined value
• rename RefinementSelect to menuSelect (needs to get some input from the team about naming)
• tests
• documentation & examples

What project are you opening a pull request for?

• instantsearch.js (use develop base)

Summary
#868

Result

[vvo]

Deploy preview ready!

Built with commit dd4d668

https://deploy-preview-2045--algolia-instantsearch.netlify.com

[Haroenv]

looks like a well done feature

[iam4x]

I've rebased on develop to make it possible to merge 👍

[bobylito]

This will be a community widget. Thanks for the contribution.

[HellPat]

Is it already available somehow?

[Haroenv]

@psren, check out https://github.com/algolia/instantsearch.js/blob/develop/dev/app/custom-widgets/vanilla/selectMenu.js

[vvo]

Seems that some good gems are only available in the dev app, should we make them available via recipes or something?

[Haroenv]

We were thinking of getting the dev app visible for sure, a nice way would be to link to the source from the published dev novel @vvo

cc @iam4x

[bobylito]

The menu select rendering is the example of the connectMenu: https://community.algolia.com/instantsearch.js/v2/connectors/connectMenu.html