Update Appendix sections of DG

[iynixil]

• minor edit to footnote in UG
• update User Stories, NFRs, Glossary in DG
• update Manual Testing section in DG

open to suggestions for user stories, NFRs and Glossary if any

Resolves #255, part of #251

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.55%. Comparing base (5aff9ba) to head (d3c0f8a).
Report is 27 commits behind head on master.

❗ Current head d3c0f8a differs from pull request most recent head 66ff70a. Consider uploading reports for the commit 66ff70a to get more accurate results

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #257   +/-   ##
=========================================
  Coverage     78.55%   78.55%           
  Complexity      846      846           
=========================================
  Files           121      121           
  Lines          2583     2583           
  Branches        262      262           
=========================================
  Hits           2029     2029           
  Misses          498      498           
  Partials         56       56           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.