feat(ligatures): adds a proposal to add ligatures

[oscargm]

Related with #182

[vfreitas-]

@oscargm I think its probably better to revert the changes on the package-lock file? As they seem not necessary for this change (probably its only a npm version difference) it would help the @tancredi review.

@tancredi You think this is a good change? If you need more context, this would allow the font to be used with the getIconId text as an inline text of the html element instead of using the unicode for example:

Json generated with fantasticon

{
  "bank-fill": 61697,
  "bank": 61698,
  "building-fill": 61699,
  "building": 61700,
  "community-fill": 61701,
  "community": 61702,
  "government-fill": 61703,
  "government": 61704
}

.my-icon {
  font-family: icons; // font family generated with fantasticon
  font-weight: normal;
  font-style: normal;
  font-size: 24px;
  display: inline-block;
  line-height: 1;
  text-transform: none;
  letter-spacing: normal;
  word-wrap: normal;
  white-space: nowrap;
  direction: ltr;

  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  -moz-osx-font-smoothing: grayscale;

  font-feature-settings: 'liga';
}

<span class="my-icon">building</span>

The html would render the icon without using the before or after pseudo elements.

[oscargm]

Yeah sure @vfreitas- no problem.

I was awaiting for @tancredi's feedback, if he agrees with the proposal I can try to continue and make a proposal for extending the configuration and fix the tests.

[jamesmsk]

waiting for this PR too!!!!!!

[oscargm]

Fixing snapshot testing here

[oscargm]

Also added a field named addLigatures in configuration and modified test accordingly

[oscargm]

@tancredi could we review the PR and merge it in case it's okay?

[lampewebdev]

Waiting for this too.