chore: convert root template to .heex #5302

Job	Run time
Build Docker image	7m 42s
file_changes	5s
Build application and assets	6m 47s
Linting / TypeScript	38s
Linting / CSS	27s
Unit tests / JavaScript / Mocha	44s
Linting / JavaScript	33s
Formatting / Elixir	3m 8s
Linting / Elixir	3m 31s
Formatting / JavaScript & TypeScript	28s
Unit tests / JavaScript & TypeScript / Jest	2m 18s
Type checks / Elixir	4m 8s
Type checks / TypeScript	44s
Unit tests / Elixir / mix coveralls.html	1m 1s
	32m 14s

Provide feedback