README: Add more contents to the "further information" section.

[pat-s]

No description provided.

[codecov-io]

Codecov Report

Merging #13871 (1a7cfb1) into master (173e512) will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #13871      +/-   ##
==========================================
+ Coverage   42.13%   42.15%   +0.02%     
==========================================
  Files         708      708              
  Lines       77190    77190              
==========================================
+ Hits        32521    32543      +22     
+ Misses      39322    39304      -18     
+ Partials     5347     5343       -4     

Impacted Files	Coverage Δ
models/repo_mirror.go	2.38% <0.00%> (-11.91%)	⬇️
modules/cron/tasks_basic.go	87.35% <0.00%> (-3.45%)	⬇️
services/mirror/mirror.go	15.78% <0.00%> (-1.11%)	⬇️
services/pull/pull.go	40.19% <0.00%> (-0.50%)	⬇️
models/error.go	38.66% <0.00%> (+0.48%)	⬆️
models/gpg_key.go	53.90% <0.00%> (+0.57%)	⬆️
models/repo_list.go	79.46% <0.00%> (+0.89%)	⬆️
modules/git/repo.go	46.73% <0.00%> (+1.00%)	⬆️
modules/git/blame.go	67.14% <0.00%> (+1.42%)	⬆️
models/issue_comment.go	45.46% <0.00%> (+1.96%)	⬆️
... and 4 more

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[6543]

good catch