Add appointment details to view window of ViewCommand

[Dominic-Khoo]

Closes #98

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...n/java/seedu/address/model/person/Appointment.java	0.00%	2 Missing ⚠️
src/main/java/seedu/address/ui/ViewWindow.java	0.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ	Complexity Δ
src/main/java/seedu/address/ui/ViewWindow.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...n/java/seedu/address/model/person/Appointment.java	72.72% <0.00%> (-7.28%)	9.00 <0.00> (ø)

[lim-jt]

LGTM, rmb to cover test cases in 1.6