PCHR-3724: Sync styles with Shoreditch

[igorpavlov-zz]

Overview

This PR syncs styles in the HRJobContract extension with Shoreditch. Please see compucorp/org.civicrm.shoreditch#110 for more info.

Technical Details

Strip out comments in dist CSS file

line_comments = false // that's why this PR introduces 2K+ deletions

Move variables and mixins to make them accessible outside namespace

/* Moved outside ##{$module} {...} */
@import 'civihr/bootstrap-variables';
@import 'bootstrap/variables';

Create a partial for Shoreditch imports

@import '../../../org.civicrm.shoreditch/scss/bootstrap/overrides/variables';
@import '../../../org.civicrm.shoreditch/scss/bootstrap/mixins/prefix';

##{$module} {
  // Still keep generic datepicker styles inside namespace
  @import '../../../org.civicrm.shoreditch/scss/angular/overrides/uib-datepicker';
}
// Import mobile datepicker styles outside namespace
@import '../../../org.civicrm.shoreditch/scss/angular/overrides/outside-namespace/uib-datepicker';

Finally include the partial

/* Also outside ##{$module} {...} */
@import 'civihr/partials/shoreditch-imports';

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According to the dist CSS file diff, there are no style changes whatsoever.