Show Toast when offline in Download

[anandwana001]

Towards #662

This is a part 1 PR where we are showing a popup if device is not connected while trying to download the offline imagery.

• When offline, show message "You are offline. Connect to download offline map imagery".

Part 2 will be

• If download fails, show error ("Connection lost") or similar.
  The part 2 will close other tickets as well where we need to build download cancel feature,

@shobhitagarwal1612 PTAL?

[codecov]

Codecov Report

Attention: Patch coverage is 36.36364% with 7 lines in your changes missing coverage. Please review.

Project coverage is 63.38%. Comparing base (243d7cd) to head (69b079a).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...flineareas/selector/OfflineAreaSelectorFragment.kt	20.00%	3 Missing and 1 partial ⚠️
...lineareas/selector/OfflineAreaSelectorViewModel.kt	50.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2990      +/-   ##
============================================
- Coverage     63.42%   63.38%   -0.05%     
- Complexity     1241     1242       +1     
============================================
  Files           267      267              
  Lines          6497     6508      +11     
  Branches        911      913       +2     
============================================
+ Hits           4121     4125       +4     
- Misses         1790     1796       +6     
- Partials        586      587       +1     

Files with missing lines	Coverage Δ
...lineareas/selector/OfflineAreaSelectorViewModel.kt	29.48% <50.00%> (+1.70%)	⬆️
...flineareas/selector/OfflineAreaSelectorFragment.kt	38.98% <20.00%> (-1.76%)	⬇️

[shobhitagarwal1612]

Are you planning to add some unit tests for this?

[anandwana001]

Are you planning to add some unit tests for this?

in second pr, for complete testing.