refactor: migrate addon package to TypeScript #488

Job	Run time
Lint	45s
Tests (ubuntu-latest, chrome)	45s
Floating Dependencies (ubuntu-latest, chrome)	51s
Type checking - [email protected]	35s
Tests - ember-lts-3.28	59s
Type checking - [email protected]	29s
Tests - ember-lts-4.4	51s
Type checking - typescript@next	31s
Tests - ember-lts-4.8	45s
Tests - ember-lts-4.12	1m 2s
Tests - ember-classic	1m 5s
Tests - ember-release	47s
Tests - ember-beta	58s
Tests - embroider-safe	59s
Tests - embroider-optimized	51s
Tests - ember-canary	51s
	13m 4s

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