Add tutorial link

[benkoshy]

Add a tutorial link.

Hopefully this will reduce the time you spend answering questions on the pagy gitter, and it will hopefully allow users to quickly find the solutions to their problems without delay.

I hope it helps.

Ben

[codecov]

Codecov Report

Merging #222 into master will increase coverage by 2.64%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           master   #222      +/-   ##
========================================
+ Coverage   97.35%   100%   +2.64%     
========================================
  Files          26     26              
  Lines         530    530              
========================================
+ Hits          516    530      +14     
+ Misses         14      0      -14

Impacted Files	Coverage Δ
lib/pagy/extras/overflow.rb	100% <0%> (ø)	⬆️
lib/pagy/extras/support.rb	100% <0%> (ø)	⬆️
lib/pagy/extras/trim.rb	100% <0%> (ø)	⬆️
lib/pagy/extras/shared.rb	100% <0%> (+16.66%)	⬆️
lib/pagy/extras/searchkick.rb	100% <0%> (+20.83%)	⬆️
lib/pagy/extras/elasticsearch_rails.rb	100% <0%> (+23.07%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5cfc10c...31f192d. Read the comment docs.