[Feature Request] Resolver for NPM Modules

[penx]

This has previously been raised as #1136 but is still an issue.

As previously raised:

Suppose we have a package installed like this:

`npm i -S @example/cards`

Now want to import from it like this within a template:

`{% import "@example/templates/birthday.html" as birthday %}`

Could the nunjucks resolver implement NPMs resolv alogrithm?

A potential solution has previously been suggested:

nunjucks.configure('node_modules');
#1136 (comment)

However, as far as I know, this doesn't use standard node_modules resolution and so would not work under several conditions:

• using npm link
• having templates in peerDependencies, as the node_modules path could not be calculated relative to the current file
• where a project has module1 as a dependency, module1 uses nunjucks, which in turn has a dependency on module2 that contains templates. Depending on the dependency tree, the templates may live in project/node_modules/module2, or project/node_modules/module1/node_modules/module2
• when using yarn pnp, node_modules does not exist at a known location on disk
• when using npm tink
• in a monorepo (e.g. using lerna or yarn workspaces), which introduces several other patterns such as linking between modules

[penx]

A possible solution would be to use the same convention as in some scss projects, in that starting a path with ~ infers using node_modules resolution:

{% import "~@example/templates/birthday.html" as birthday %}