Add JSDoc as good practice

[sabau]

Description:

• examples of documentation in some modules
• added command doc to package.json
• explicitely working only on app/src files
• currently ignoring the generated documentation, until it's perceived as really useful

Closes #1739

Once we are in a presentable state we may link this in the wiki along with our README

❤️ Thank you!

---

• Added entries in CHANGELOG.md with issue # and GitHub username
• Reviewed Files changed in the github PR explorer

[fedekunze]

LGTM

[codecov]

Codecov Report

Merging #1813 into develop will decrease coverage by <.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #1813      +/-   ##
===========================================
- Coverage    94.85%   94.84%   -0.01%     
===========================================
  Files          123      122       -1     
  Lines         2954     2949       -5     
  Branches       121      121              
===========================================
- Hits          2802     2797       -5     
  Misses         143      143              
  Partials         9        9

Impacted Files	Coverage Δ
app/src/renderer/scripts/num.js	100% <ø> (ø)	⬆️
app/src/renderer/components/wallet/PageWallet.vue	100% <ø> (ø)	⬆️
app/src/renderer/vuex/store.js	100% <ø> (ø)	⬆️
app/src/renderer/App.vue	100% <ø> (ø)	⬆️
app/src/renderer/main.js	79.03% <ø> (ø)	⬆️
app/src/renderer/google-analytics.js	33.33% <ø> (ø)	⬆️

[codecov]

Codecov Report

Merging #1813 into develop will decrease coverage by <.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #1813      +/-   ##
===========================================
- Coverage    94.85%   94.84%   -0.01%     
===========================================
  Files          123      122       -1     
  Lines         2954     2949       -5     
  Branches       121      121              
===========================================
- Hits          2802     2797       -5     
  Misses         143      143              
  Partials         9        9

Impacted Files	Coverage Δ
app/src/renderer/scripts/num.js	100% <ø> (ø)	⬆️
app/src/renderer/components/wallet/PageWallet.vue	100% <ø> (ø)	⬆️
app/src/renderer/vuex/store.js	100% <ø> (ø)	⬆️
app/src/renderer/App.vue	100% <ø> (ø)	⬆️
app/src/renderer/main.js	79.03% <ø> (ø)	⬆️
app/src/renderer/google-analytics.js	33.33% <ø> (ø)	⬆️