Update `ember-cli-babel` to version 7

[boris-petrov]

This is the only plugin that I use that still uses ember-cli-babel 6 so I decided to update it. Not sure if this is enough or more changes are needed to the plugin?

cc @vitch

[vitch]

Honestly I haven't used this plugin in many years. If you are using it and it still works for you with this change I'm happy to merge and release...

[vitch]

Although it looks like Travis is unhappy because:

The command "eval yarn --frozen-lockfile " failed.

[boris-petrov]

I was just trying to figure that out. Any ideas what that is and why it fails?

[vitch]

Actually - I think the real error is:

The engine "node" is incompatible with this module. Expected version "8.* || 10.* || >= 12.*"

I set my node and yarn versions to the same as TravisCI via volta (6.17.1 and 1.3.2 respectively) and got the same error.

Maybe you can update node_js: in the travis.yml too?

[boris-petrov]

Done. But this means a new major version. And while we're at it, we could do other version updates I guess?

[boris-petrov]

@vitch - this is ready for merging. I moved a few things around and updated the used webfonts-generator library. The Node requirement had to be updated to version 12 because of ttf2woff2 - here is a failing Travis build for proof.

I tried out the branch, it seems to work great. So a new (major) release will be appreciated! :) Thanks!