Enable support for IntelliJ compatible place holders in license header templates

IntelliJ supports the following format$today.year for injecting the current year in the license header. Since the syntax for spotless is $YEAR; they are not compatible.

Since IntelliJ can auto inject this while creating new files, it would be convenient to have a single copyright template for both.

Could we enable support for $today.year? If we agree on the solution I can send a PR.

Thanks!
Sameer