Adds "useCurrentBreakpoints" hook

[kettanaito]

Changes

• Adds useCurrentBreakpoints hook

Issues

• Closes Add "useBreakpoint" hook #279

Release version

• internal (no release required)
• patch (bug fixes)
• minor (backward-compatible changes)
• major (backward-incompatible, breaking changes)

Contributor's checklist

• My branch is up-to-date with the latest master

• I ran yarn verify to see the build and tests pass

• Remove the useBreakpointChange hook

[kettanaito]

Returning a list of breakpoint names, because it's possible for multiple breakpoints to match a single state of the viewport:

Layout.configure({
  breakpoints: {
    portrait: {
      orientation: 'portrait'
    },
    mobile: {
      maxWidth: 576
    }
  }
})

On a viewport with the width of 500px both portrait and mobile breakpoints would match.

[kettanaito]

I'm currently in doubt whether this hooks bears any user value. Discussion in #279