Add text or lines template plugin

[RhetTbull]

See this post. It would be helpful to be able to directly access the lines of text in a file as part of the metadata, for example to grab the first line. A {lines} plugin would let user access the lines in the file as part of the template. For example:

{lines:0} grabs first line while {lines:-1} grabs last line. {lines:0:1} grabs lines 0 & 1.