add line number token that can be passed into "open" command

[pbkhrv]

If a match is on a line inside the note, being able to open that file on that line might be helpful (NV does that IIRC).
For instance, gedit accepts line number as argument, so the command would look like this:

gedit %fn +%ln

where %fn is "note file path" and %ln is "matching note line number"

Possible issues:

• if don't have line number, the command would look different - have 2 diff commands in configuration? that gets a little complicated.

Answer might come after I and others use the extension for a while.