Add --select-lines option

[bkuhlmann]

Overview

Would it be possible to allow Silicon to specify the lines of a file to screenshot in addition to the lines highlighted? I ask because I often find I want to select a snippet of code for illustration and sharing but also highlight maybe a line or two within the selected lines.

Screenshots/Screencasts

Steps to Recreate

At the moment, I have to do the following:

1. Copy Lines 11-13 to a file called snippet.rb.
2. Run: silicon --language rb --highlight-lines 2 --to-clipboard snippet.rb
3. Run: rm -f snippet.rb.

Example result (with a few more options thrown in not shown above):

Desired Behavior

It would be neat to simplify the steps presented above to a single step. Example:

1. Run: silicon --language rb --select-lines 11-13 --highlight-lines 12 --to-clipboard lib/xdg/environment.rb

It could also be handy to have an option for --line-count-start 1 in case someone didn't want the count to start at 11 from the original source but start at 1 instead.