Building the code results in a build error

[mariuslazar93]

Hi all,

We started to encounter a build error from ember-key-manager since this morning.

Steps to reproduce:

1. Clone repo
2. run "npm i"
3. run "npm run build"

Results in the following error:
`Build Error (broccoli-persistent-filter:Babel > [Babel: ember-key-manager]) in ember-key-manager/modifiers/key-macro.ts

/Users/marius.lazar/Work/frontend/ember-key-manager/ember-key-manager/modifiers/key-macro.ts: Abstract methods can only appear within an abstract class. (28:2)`

Node v12