add render attached file macro

[wate]

Add new macro to render attached file. Could you please check and merge?

Example1

{{plantuml_attach(diagram.pu)}}

Example2

with image format

{{plantuml_attach(diagram.pu, format=svg)}} 

[paulvi]

Would this macro find diagram.pu attach in any project?

[wate]

@paulvi Macro arguments are files attached to the corresponding wiki or ticket