Change PersonListCard index to JetBrains Mono SemiBold font

[aureliony]

Closes #151

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 76.94%. Comparing base (94da53e) to head (e94eb79).

Files	Patch %	Lines
src/main/java/seedu/address/ui/UiManager.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #180      +/-   ##
============================================
- Coverage     76.99%   76.94%   -0.05%     
  Complexity      515      515              
============================================
  Files            75       75              
  Lines          1595     1596       +1     
  Branches        143      143              
============================================
  Hits           1228     1228              
- Misses          337      338       +1     
  Partials         30       30              

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[bryanyee33]

LGTM