add content len field

[dogancanbakir]

Closes #1032

[Mzack9999]

From the issue, if the goal is mostly checking if the body is empty or not I think it's better to directly access it via jq, as the Content-Length header might be misleading or inconsistent as well. For example:

katana -u https://gmail.com | jq 'select(.body != "")'

What do you think?

[dogancanbakir]

Yes, but in this case, we're calculating the len from the body -mentioning @Sab0tag3d for the discussion.

[Sab0tag3d]

@Mzack9999
Well, my goal is mostly to understand the size of the content on the pages.
It's really helpful to detect some anomaly contents.

Besides, if we would use tool like jq, we need to store html bodies in report (in my case it's json file).
I don't do it because of space, in memory and on disk.
Also, sometimes JSON is broken because of body, and can't be parsed. I think it's because of maximum response size to read option, but haven't done investigation yet.