Need a way to _not_ escape markup in external args

[reedstrm]

When translating complex pages on a website, we ran into a problem where we have variable content that contains HTML markup, that is passed as l10-n-args attribute values in the DOM. This content is fro a trusted/vetted source, so we don't need the sanitizeArgs escaping. However, there doesn't seem to be a way to avoid it. Since the args are sanitized when the keys are fetched from context, before they are passed to translation, I don't see a way to add a special TrustedText type. I was considering a builtin function HTML() or some such that would reverse the santiizeArgs replacements.

[zbraniecki]

@stasm - was it a deliberate choice to not let args be passed unsanitized? I remember some conversation about it during the security review, but I do not remember the outcome.