Added Table of Contents to long documentation pages

[6543]

A redo of #13836

use new introduced shortcode (https://gitea.com/gitea/theme/pulls/90)

[codecov-io]

Codecov Report

Merging #13890 (f64a06c) into master (682f0b0) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #13890   +/-   ##
=======================================
  Coverage   42.25%   42.26%           
=======================================
  Files         708      708           
  Lines       77191    77191           
=======================================
+ Hits        32620    32626    +6     
+ Misses      39211    39208    -3     
+ Partials     5360     5357    -3     

Impacted Files	Coverage Δ
modules/log/event.go	58.96% <0.00%> (-0.95%)	⬇️
services/pull/check.go	51.09% <0.00%> (-0.73%)	⬇️
models/error.go	39.47% <0.00%> (+0.48%)	⬆️
modules/process/manager.go	75.00% <0.00%> (+2.50%)	⬆️
modules/indexer/stats/db.go	52.17% <0.00%> (+8.69%)	⬆️
modules/indexer/stats/queue.go	76.47% <0.00%> (+11.76%)	⬆️

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[pat-s]

A note on the new toc shortcode: h1 are not processed and pages should be updated to start at h2 by default so that all headers are included in the ToC.

I will do that now.