Allow including a specific number of lines in the beginning and end of files

[kantord]

In some use cases it might be useful to get more context about a result file by adding a specific number of lines in the beginning or end of the file. This could provide additional understanding regarding how the file is structured, etc. In order to do this, we could provide an argument for a special type of context line which is defined in relation to the end/beginning of the file that a result is coming from, rather than in relation to result lines within a file