add RunAfterTimeout & RunOnInterval

[maddalax]

1. Adds RunAfterTimeout & RunOnInterval

Usage:

h.Div(
    h.OnLoad(
	  h.RunOnInterval(time.Second,
            js.ConsoleLog("this runs a command every 1s"),
            js.SetInnerHtml(h.Div()),
	  ),
    )
)

h.Div(
    h.OnLoad(
	  h.RunAfterTimeout(time.Second,
            js.ConsoleLog("this runs a command once after a second"),
            js.SetInnerHtml(h.Div()),
	  ),
    )
)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.91%. Comparing base (a1af01a) to head (ef83e34).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #75      +/-   ##
==========================================
+ Coverage   72.66%   72.91%   +0.24%     
==========================================
  Files          33       33              
  Lines        2817     2843      +26     
==========================================
+ Hits         2047     2073      +26     
  Misses        729      729              
  Partials       41       41              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.