Extract tag function and Edit AboutUs

[YeoBohShin]

Made the Tag function isolated from Edit function.

But now still tagging with index instead of student
number.

Edited the About us to include all members

Added each member's skeleton for portfoilio

[codecov]

Codecov Report

Merging #5 (eb197b0) into master (5517080) will increase coverage by 0.47%.
The diff coverage is 89.36%.

❗ Current head eb197b0 differs from pull request most recent head 2a231a7. Consider uploading reports for the commit 2a231a7 to get more accurate results

@@             Coverage Diff              @@
##             master       #5      +/-   ##
============================================
+ Coverage     75.26%   75.74%   +0.47%     
- Complexity      419      437      +18     
============================================
  Files            71       73       +2     
  Lines          1338     1385      +47     
  Branches        126      133       +7     
============================================
+ Hits           1007     1049      +42     
  Misses          301      301              
- Partials         30       35       +5     

Files	Coverage Δ
.../seedu/address/logic/parser/AddressBookParser.java	100.00% <100.00%> (ø)
...ain/java/seedu/address/logic/parser/CliSyntax.java	85.71% <100.00%> (+2.38%)	⬆️
.../java/seedu/address/logic/commands/TagCommand.java	92.59% <92.59%> (ø)
...a/seedu/address/logic/parser/TagCommandParser.java	83.33% <83.33%> (ø)