support jsoniter

[DarthPestilane]

Add a subpackage "json" and change "encoding/json" to "github.com/labstack/echo/json"

[codecov]

Codecov Report

Merging #1204 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1204   +/-   ##
=======================================
  Coverage   81.52%   81.52%           
=======================================
  Files          25       25           
  Lines        1921     1921           
=======================================
  Hits         1566     1566           
  Misses        248      248           
  Partials      107      107

Impacted Files	Coverage Δ
context.go	74.31% <ø> (ø)	⬆️
bind.go	86.3% <ø> (ø)	⬆️

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[im-kulikov]

Try to hold a benchmark, for example, taking from here.
In my case, it turned out that there is no profit as such, on the contrary, a loss in performance.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.