Add help modal to add server screen

[thornbill]

Adds a help icon to the add server screen that opens a modal when pressed.

Add Server Screen	Help Modal

[sonarcloud]

SonarCloud Quality Gate failed.

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
7.8% Duplication

[codecov]

Codecov Report

Merging #246 (997cd99) into master (225e99b) will decrease coverage by 0.93%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #246      +/-   ##
==========================================
- Coverage   33.68%   32.74%   -0.94%     
==========================================
  Files          33       36       +3     
  Lines         662      681      +19     
  Branches      133      134       +1     
==========================================
  Hits          223      223              
- Misses        397      416      +19     
  Partials       42       42              

Impacted Files	Coverage Δ
App.js	0.00% <ø> (ø)
constants/Links.js	0.00% <0.00%> (ø)
navigation/RootNavigator.js	0.00% <0.00%> (ø)
screens/AddServerScreen.js	0.00% <0.00%> (ø)
screens/ServerHelpScreen.js	0.00% <0.00%> (ø)

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