[CHANGE] Calculate the entropy of files bigger than 1GB (just read first 1 GB, and calculate entropy of this part)

[steph-nb]

(copy of codeberg.org issue nr. 4)

Hi Steffen,

as promised some weeks ago in Marbach :-)

For files bigger than 1GB, one could use just a 1GB part of the file (this should be representative enough, I guess?).
E.g.: just read the first 1GB, and calculate the entropy of it.

BR,
Stephan