es6 build: stricter targets to eliminate async/await transformations

[ibgreen]

The current set of targets include too many transforms. In particular, async/await gets transformed and generator runtime gets included which completely defeats the clean async debugging experience in Chrome.

At this point, the goal is to get rid of

  transform-async-to-generator { "ios":"10.3", "safari":"10.1" }

As can be seen, additional plugin reduction will not be possible until end of year when Node 8 ends LTS.

After the change the following plugins are picked:

  transform-template-literals { "ios":"12", "safari":"12" }
  transform-function-name { "edge":"18" }
  transform-dotall-regex { "edge":"18", "firefox":"60", "node":"8" }
  proposal-async-generator-functions { "edge":"18", "node":"8" }
  proposal-object-rest-spread { "edge":"18", "node":"8" }
  proposal-unicode-property-regex { "edge":"18", "firefox":"60", "node":"8" }
  proposal-json-strings { "chrome":"64", "edge":"18", "firefox":"60", "node":"8" }
  proposal-optional-catch-binding { "chrome":"64", "edge":"18", "node":"8" }
  transform-named-capturing-groups-regex { "edge":"18", "firefox":"60", "node":"8" }

Before the change

  transform-template-literals { "ios":"10.3", "safari":"10.1" }
  transform-function-name { "edge":"15" }
  transform-dotall-regex { "chrome":"60", "edge":"15", "firefox":"53", "ios":"10.3", "node":"8", "safari":"10.1" }
  transform-unicode-regex { "ios":"10.3", "safari":"10.1" }
  transform-parameters { "edge":"15" }
  transform-async-to-generator { "ios":"10.3", "safari":"10.1" }
  proposal-async-generator-functions { "chrome":"60", "edge":"15", "firefox":"53", "ios":"10.3", "node":"8", "safari":"10.1" }
  proposal-object-rest-spread { "edge":"15", "firefox":"53", "ios":"10.3", "node":"8", "safari":"10.1" }
  proposal-unicode-property-regex { "chrome":"60", "edge":"15", "firefox":"53", "ios":"10.3", "node":"8", "safari":"10.1" }
  proposal-json-strings { "chrome":"60", "edge":"15", "firefox":"53", "ios":"10.3", "node":"8", "safari":"10.1" }
  proposal-optional-catch-binding { "chrome":"60", "edge":"15", "firefox":"53", "ios":"10.3", "node":"8", "safari":"10.1" }
  transform-named-capturing-groups-regex { "chrome":"60", "edge":"15", "firefox":"53", "ios":"10.3", "node":"8", "safari":"10.1" }

[ibgreen]

0.0.28