feat(accordion): add key navigation to accordion

[ghost]

1. I've changed html template in accordion component to add option:

• switch between accordion titles by pressing tab button
  
• open/close accordion's content by Enter and Space button:
  when accordion title is focused, press Enter or Space button - and accordion's content open or close.
  

You can try it in accordion (component) section in the demo.

closes #3992

[codecov]

Codecov Report

Merging #3993 into development will decrease coverage by 0.04%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           development    #3993      +/-   ##
===============================================
- Coverage        72.25%   72.21%   -0.05%     
===============================================
  Files              252      252              
  Lines             8237     8237              
  Branches          1565     1565              
===============================================
- Hits              5952     5948       -4     
- Misses            1865     1867       +2     
- Partials           420      422       +2

Impacted Files	Coverage Δ
src/chronos/i18n/pl.ts	72.22% <0%> (-11.12%)	⬇️

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[YevheniiaMazur]

Please, add link to issue, due to what this PR was created.

[ghost]

@YevheniiaMazur fixed

[YevheniiaMazur]

Not clear: do you mean open accordion with Enter key and close it by Space key?

[ghost]

@YevheniiaMazur I've change description

[YevheniiaMazur]

Tested, looks good