Implement the Storage and GUI for Appointment

[MaYuehan]

Implement the GUI for Appointment functions. #55
Add appointment list to storage. #66
Will fix the Junit test for createAptCommandTest class later.

[codecov]

Codecov Report

Attention: Patch coverage is 53.25444% with 79 lines in your changes are missing coverage. Please review.

Project coverage is 68.84%. Comparing base (027086d) to head (a4ab407).

Files	Patch %	Lines
src/main/java/vitalconnect/MainApp.java	0.00%	13 Missing ⚠️
src/main/java/vitalconnect/ui/MainWindow.java	0.00%	13 Missing ⚠️
src/main/java/vitalconnect/ui/AppointmentCard.java	0.00%	12 Missing ⚠️
...ain/java/vitalconnect/ui/AppointmentListPanel.java	0.00%	12 Missing ⚠️
.../vitalconnect/logic/commands/CreateAptCommand.java	38.46%	7 Missing and 1 partial ⚠️
src/main/java/vitalconnect/model/ModelManager.java	33.33%	5 Missing and 1 partial ⚠️
src/main/java/vitalconnect/model/Appointment.java	54.54%	1 Missing and 4 partials ⚠️
src/main/java/vitalconnect/model/UserPrefs.java	83.33%	1 Missing and 1 partial ⚠️
...a/vitalconnect/storage/JsonAdaptedAppointment.java	88.23%	1 Missing and 1 partial ⚠️
...a/vitalconnect/storage/JsonAppointmentStorage.java	90.47%	2 Missing ⚠️
... and 3 more

Additional details and impacted files

@@             Coverage Diff              @@
##             master      #61      +/-   ##
============================================
- Coverage     71.02%   68.84%   -2.19%     
- Complexity      559      578      +19     
============================================
  Files            93       98       +5     
  Lines          1826     1961     +135     
  Branches        192      203      +11     
============================================
+ Hits           1297     1350      +53     
- Misses          455      529      +74     
- Partials         74       82       +8     

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[Ella-e]

LGTM

[Ella-e]

Should be 'boolean doesIcExist(String nric)'