Support template literals

[bajtos]

Extend strong-globalize to support template literals via tagged template literals.

Sample usage:

const {_}  = require('strong-globalize')();

const name = 'world';
console.log(_`Hello ${name}`);

Preliminary list of tasks:

• When gathering strings to potentially localize, look for template literals and convert them into messages with indexed placeholders. In the example above, the following messages entry should be created: Hello {0}
• Implement _ as a tag function applying localization under the hood.

[bajtos]

An alternative to consider: modify g.f to support two invocations forms:

g.f('Hello %s', name);
g.f`Hello ${name}`;