feature: add loading animation when search data is loading

[uchuhimo]

When clicking search button first time, it will spend a long time loading search data if search.xml is large (usually 5-10 seconds), without any response. I add a loading animation to indicate the loading process. Demo:

[ivan-nginx]

GJ! I'll test it soon. Wait for response.

[ivan-nginx]

@uchuhimo loading work perfectly, u can test it on my last example site.

But, it is really need to add *.svg picture, if we already have fontawesome icons? Can u check this page, there are animation icons and may be just use them instead of svg? If it's possible, of course. And if it will be better.

[uchuhimo]

@ivan-nginx Thank you for reminding me, I will try and update the pull request if it's possible.

[ivan-nginx]

@uchuhimo firstly, need to test and try it. If FA will better, need to use it, i think.

[uchuhimo]

@ivan-nginx It works. Demo:

The appearance is similar. We can reduce the svg picture if we use animation icon.

[ivan-nginx]

@uchuhimo ok, do how it will be better. ;)

[uchuhimo]

@ivan-nginx I have updated this pull request, check it please

[ivan-nginx]

@uchuhimo yeah, it's work fine and no need svg icon. Well done and thanks!