Move theme helpers and some stylesheets to proper locations

src/common/AppUpdateBanner.scss

@@ -1,4 +1,4 @@
-@import '../utils/base';
+@import '@shlinkio/shlink-frontend-kit/base';
 @import '../utils/mixins/horizontal-align';
 
 .app-update-banner.app-update-banner {

src/common/Home.scss

@@ -1,4 +1,4 @@
-@import '../utils/base';
+@import '@shlinkio/shlink-frontend-kit/base';
 @import '../utils/mixins/vertical-align';
 
 $mainCardWidth: 720px;

src/common/MainHeader.scss

@@ -1,4 +1,4 @@
-@import '../utils/base';
+@import '@shlinkio/shlink-frontend-kit/base';
 
 .main-header.main-header {
   color: white;

src/common/NoMenuLayout.scss

@@ -1,4 +1,4 @@
-@import '../utils/base';
+@import '@shlinkio/shlink-frontend-kit/base';
 
 .no-menu-wrapper {
   padding: 15px 0 0;

src/common/ShlinkVersionsContainer.scss

@@ -1,4 +1,4 @@
-@import '../utils/base';
+@import '@shlinkio/shlink-frontend-kit/base';
 
 .shlink-versions-container--with-sidebar {
   margin-left: 0;

src/common/ShlinkWebComponentContainer.scss

@@ -1,4 +1,4 @@
-@import '../utils/base';
+@import '@shlinkio/shlink-frontend-kit/base';
 
 .menu-layout__swipeable {
   height: 100%;

src/common/img/ShlinkLogo.tsx

@@ -1,4 +1,4 @@
-import { MAIN_COLOR } from '../../utils/theme';
+import { MAIN_COLOR } from '@shlinkio/shlink-frontend-kit';
 
 export interface ShlinkLogoProps {
   color?: string;

src/common/react-tag-autocomplete.scss

@@ -1,4 +1,4 @@
-@import '../utils/base';
+@import '@shlinkio/shlink-frontend-kit/base';
 
 .react-tags {
   position: relative;