Implement custom lightweight modal #230

Introduce a brand new lightweight and efficient modal component. It is
designed to be visually similar to the previous one to not introduce a
change in feel of the application in a patch release, but behind the
scenes it features:

- Enhanced application speed and reduced bundle size.
- New flexbox-driven layout, eliminating JS calculations.
- Composition API ready for Vue 3.0 #230.

Other changes:

- Adopt idiomatic Vue via `v-modal` binding.
- Add unit tests for both the modal and dialog.
- Remove `vue-js-modal` dependency in favor of the new implementation.
- Adjust modal shadow color to better match theme.
- Add `@vue/test-utils` for unit testing.

src/presentation/components/Shared/Modal/ModalOverlay.vue

@@ -0,0 +1,65 @@
+<template>
+  <transition
+    name="modal-overlay-transition"
+    @after-leave="onAfterTransitionLeave"
+  >
+    <div
+      v-if="show"
+      class="modal-overlay-background"
+      aria-expanded="true"
+      @click.self.stop="onClick"
+    />
+  </transition>
+</template>
+
+<script lang="ts">
+import { defineComponent } from 'vue';
+
+export default defineComponent({
+  props: {
+    show: {
+      type: Boolean,
+      default: false,
+    },
+  },
+  emits: [
+    'click',
+    'transitionedOut',
+  ],
+  setup(_, { emit }) {
+    function onAfterTransitionLeave() {
+      emit('transitionedOut');
+    }
+
+    function onClick() {
+      emit('click');
+    }
+
+    return {
+      onAfterTransitionLeave,
+      onClick,
+    };
+  },
+});
+
+</script>
+
+<style scoped lang="scss">
+@use "@/presentation/assets/styles/main" as *;
+
+$modal-overlay-transition-duration: 50ms;
+$modal-overlay-color-background: $color-on-surface;
+
+.modal-overlay-background {
+  position: fixed;
+  box-sizing: border-box;
+  left: 0;
+  top: 0;
+  width: 100%;
+  height: 100vh;
+  background: rgba($modal-overlay-color-background, 0.3);
+  opacity: 1;
+}
+
+@include fade-slide-transition('modal-overlay-transition', $modal-overlay-transition-duration);
+</style>