Add script tags from config to body

[everett980]

Which problem is this PR solving?

• We need the ability to run non-OSS code on the UI without treating Jaeger UI as a component library.

Short description of the changes

• Adds scripts field to config, which are added to the document body.
• Initially only inline scripts are supported, as the config is a JSON and we need the ability to define an onLoad function if we were to use a src

[codecov]

Codecov Report

Merging #455 into master will increase coverage by 0.07%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #455      +/-   ##
==========================================
+ Coverage   88.81%   88.88%   +0.07%     
==========================================
  Files         184      185       +1     
  Lines        4239     4248       +9     
  Branches     1021     1023       +2     
==========================================
+ Hits         3765     3776      +11     
+ Misses        428      426       -2     
  Partials       46       46

Impacted Files	Coverage Δ
packages/jaeger-ui/src/components/App/index.js	100% <100%> (ø)	⬆️
...ges/jaeger-ui/src/utils/config/process-scripts.tsx	100% <100%> (ø)
...eViewer/TimelineHeaderRow/TimelineViewingLayer.tsx	91.52% <0%> (+3.38%)	⬆️

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[yurishkuro]

if we have some README that describes the syntax of the config file, please add a note to it about the new element.

Otherwise, it should be added to the docs on the website.

[everett980]

@yurishkuro the only documentation for the config json in this repo is a link to jaegertracing.io, otherwise we rely on type definitions.
I'll update the linked page tomorrow.