Add global spinner to UiService

[duluca]

[mamadoutoure]

Hi, I can take care of this issue... if it’s ok for you I can fix it in ng8 branch, or on a brand new branch

[duluca]

@mamadoutoure that'd be a great addition to the ng8 branch! Bonus points if you can somehow incorporate the lemon logo from icons/lemon.svg in a static way or if you're feeling up to it the svg element in lemon-rater in a more dynamic way. It'd definitely add some zest to the implementation. It'd also be a great demonstration of how to implement a custom branded loading! Thanks

[mamadoutoure]

@duluca. Do you mean you want the lemon logo act as a spinner (ie having it rotate when the page is loading)?

[duluca]

It's totally up to you!