bitswap/client: explain what the options do

[hsanjuan]

Added godoc explanation of what the client options do in more detail, since given information was useless.

[codecov]

Codecov Report

Merging #488 (9999444) into main (fe55533) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #488      +/-   ##
==========================================
+ Coverage   65.58%   65.61%   +0.03%     
==========================================
  Files         207      207              
  Lines       25540    25540              
==========================================
+ Hits        16750    16758       +8     
+ Misses       7323     7315       -8     
  Partials     1467     1467              

Files	Coverage Δ
bitswap/client/client.go	88.12% <100.00%> (ø)

... and 12 files with indirect coverage changes

[Jorropo]

Let's not write text that is gonna be outdated once we change this, I people to do 1 click if they want to follow the constant.

addressed