Add full Unicode support

[jmigual]

If add an unicode character then the filter fails to render in pandoc and I have to manually stop the compilation

Example:

graph LR;

I0 --> I1(✋);

Loading

This does not render

But if instead I do:

graph LR;

I0 --> I1(A);

I get

[jmigual]

I just discovered that using the text in quotes properly renders the unicode.
Closing it then