Add UI for searchmode

[jan-kai1]

For #164
Not sure how to do testcase for MainWindow

[codecov]

Codecov Report

Attention: Patch coverage is 30.43478% with 16 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/main/java/seedu/address/ui/MainWindow.java	0.00%	16 Missing ⚠️

Files with missing lines	Coverage Δ	Complexity Δ
...rc/main/java/seedu/address/logic/LogicManager.java	70.00% <100.00%> (+2.14%)	5.00 <2.00> (+2.00)
src/main/java/seedu/address/model/Model.java	100.00% <ø> (ø)	1.00 <0.00> (ø)
...rc/main/java/seedu/address/model/ModelManager.java	100.00% <100.00%> (ø)	33.00 <5.00> (+2.00)
src/main/java/seedu/address/ui/MainWindow.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)

[cshao02]

LGTM!