feat: implement Splash screen

[goga-m]

Summary

Show splash screen on launch until initial data is loaded.
https://trello.com/c/kmWaiidX/191-implement-splash-screen

Checklist

• Documentation (if necessary)
• Tests (if necessary)
• Ready to be merged

[codecov]

Codecov Report

Merging #2617 into 3.0-react will not change coverage.
The diff coverage is 100.00%.

@@              Coverage Diff              @@
##           3.0-react     #2617     +/-   ##
=============================================
  Coverage     100.00%   100.00%             
=============================================
  Files             24       251    +227     
  Lines            142      3001   +2859     
  Branches          18       544    +526     
=============================================
+ Hits             142      3001   +2859     

Flag	Coverage Δ
#unit	100.00% <100.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/app/components/Button/Button.tsx	100.00% <ø> (ø)
src/app/App.tsx	100.00% <100.00%> (ø)
src/app/components/Address/Address.tsx	100.00% <100.00%> (ø)
src/app/components/Alert/Alert.tsx	100.00% <100.00%> (ø)
src/app/components/Amount/Amount.tsx	100.00% <100.00%> (ø)
src/app/components/Avatar/Avatar.tsx	100.00% <100.00%> (ø)
src/app/components/Badge/Badge.tsx	100.00% <100.00%> (ø)
src/app/components/Breadcrumbs/Breadcrumbs.tsx	100.00% <100.00%> (ø)
src/app/components/Card/Card.tsx	100.00% <100.00%> (ø)
src/app/components/Card/CardControl.tsx	100.00% <100.00%> (ø)
... and 273 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1cd404d...5549f0a. Read the comment docs.