Add background color to SectionLabel

[kyleleow]

What kind of PR is this?:

/kind feature

What this PR does / why we need it:

• To improve UI when scrolling in Dex screen

Which issue(s) does this PR fixes?:

Fixes #497

Additional comments?:

Not tested on Android device

[codeclimate]

Code Climate has analyzed commit 3c96740 and detected 0 issues on this pull request.

View more on Code Climate.

[codecov]

Codecov Report

Merging #503 (3c96740) into main (73fa3a1) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #503   +/-   ##
=======================================
  Coverage   87.18%   87.18%           
=======================================
  Files         113      113           
  Lines        1904     1904           
  Branches      304      305    +1     
=======================================
  Hits         1660     1660           
  Misses        244      244           

Impacted Files	Coverage Δ
app/components/SectionTitle.tsx	100.00% <ø> (ø)
app/components/HeaderTitle.tsx	85.18% <0.00%> (ø)

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[netlify]

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[defichain-bot]

Build preview for DeFi Wallet is ready!

Built with commit d02fad2

https://expo.io/@defichain/wallet?release-channel=pr-preview-503

[cypress]

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Test summary

132 • 0 • 0 • 0

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Run details

Project	wallet
Status	Passed
Commit	d02fad2 ℹ️
Started	Aug 9, 2021 6:23 AM
Ended	Aug 9, 2021 6:45 AM
Duration	22:09 💡
OS	Linux Ubuntu - 20.04
Browser	Chrome 92

View run in Cypress Dashboard ➡️

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