Can't indent inside doc strings

[danielmatz]

When inside a multi-line string (like a doc string), julia-mode allows you to manually indent. This is useful for writing signatures in doc strings. With julia-ts-mode, indentation is locked to the beginning of the line of the parent (I think).

For example, in the following case, with point represented by |, trying to indent just keeps point where it's at.

function foo()
    x = """
    |
    """
end