feat(sortable): add support for custom item templates

[valorkin]

refs #1554

[codecov-io]

Codecov Report

Merging #1580 into development will increase coverage by <.01%.

@@               Coverage Diff               @@
##           development    #1580      +/-   ##
===============================================
+ Coverage        84.96%   84.96%   +<.01%     
===============================================
  Files               82       82              
  Lines             2301     2302       +1     
  Branches           298      298              
===============================================
+ Hits              1955     1956       +1     
  Misses             246      246              
  Partials           100      100

Impacted Files	Coverage Δ
src/sortable/sortable.component.ts	100% <100%> (ø)	✅

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