According to this esdiscuss discussion, it is possible in ECMAScript 6 to define multiline strings without having to place subsequent lines of the string at the very beginni
As Šime Vidas states, functions can be used as a tag, and invoked by just placing it in front of the template string.
A number of NPM modules exist to do this, and will cover many edge cases that would be hard to cover yourself. The main two are:
dedent, 4 million weekly downloads, last updated 4 years ago
endent, 2.5 thousand weekly downloads, updated 4 months ago