Add env badge when outside prod

[steffendsommer]

Fixes #95

[codecov]

Codecov Report

Merging #103 into vapor-3 will not change coverage.
The diff coverage is 0%.

@@          Coverage Diff           @@
##           vapor-3   #103   +/-   ##
======================================
  Coverage        0%     0%           
======================================
  Files           22     22           
  Lines          924    929    +5     
======================================
- Misses         924    929    +5

Impacted Files	Coverage Δ
Sources/AdminPanel/Configs/AdminPanelConfig.swift	0% <0%> (ø)	⬆️
Sources/AdminPanel/Tags/AdminPanelConfigTag.swift	0% <0%> (ø)	⬆️
...rces/AdminPanel/Providers/AdminPanelProvider.swift	0% <0%> (ø)	⬆️

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