Implement inlining content of external file to policy

[Mielek]

Proposal

It would be beneficial to be able to inline external files in policy document. It would allow maintaining those files separately from policy.

Example of C# code:

context.SetBody(File.ReadAllText("body.liquid"), new SetBodyConfig() { Template = "liquid" });

Compiled to

<set-body template="liquid">
  {% if user %}
    Hello {{ user.name }}!
  {% endif %}
</set-body>

Component

Authoring library, Compiler