Restructure project directories (#333)

`/client/web` -> `/frontend`
`/client/cli` -> *delete for now*
`/client/native` -> *delete for now*
`/core/editor` -> `/editor`
`/core/document` -> `/graphene`
`/core/renderer` -> `/charcoal`
`/core/proc-macro` -> `/proc-macros` *(now plural)*

frontend/src/components/widgets/buttons/PopoverButton.vue

@@ -0,0 +1,83 @@
+<template>
+	<div class="popover-button">
+		<IconButton :action="handleClick" :icon="icon" :size="16" data-hover-menu-spawner />
+		<FloatingMenu :type="MenuType.Popover" :direction="MenuDirection.Bottom" ref="floatingMenu">
+			<slot></slot>
+		</FloatingMenu>
+	</div>
+</template>
+
+<style lang="scss">
+.popover-button {
+	display: inline-block;
+	position: relative;
+	width: 16px;
+	height: 24px;
+	flex: 0 0 auto;
+
+	.floating-menu {
+		left: 50%;
+	}
+
+	.icon-button {
+		width: 100%;
+		height: 100%;
+		padding: 0;
+		outline: none;
+		border: none;
+		border-radius: 2px;
+		vertical-align: top;
+		background: var(--color-1-nearblack);
+		fill: var(--color-e-nearwhite);
+
+		&:hover {
+			background: var(--color-6-lowergray);
+			fill: var(--color-f-white);
+		}
+	}
+
+	// TODO: Refactor this and other complicated cases dealing with joined widget margins and border-radius by adding a single standard set of classes: joined-first, joined-inner, and joined-last
+	div[class*="-input"] + & {
+		margin-left: 1px;
+
+		.icon-button {
+			border-radius: 0 2px 2px 0;
+		}
+	}
+}
+</style>
+
+<script lang="ts">
+import { defineComponent } from "vue";
+import IconButton from "@/components/widgets/buttons/IconButton.vue";
+import FloatingMenu, { MenuDirection, MenuType } from "@/components/widgets/floating-menus/FloatingMenu.vue";
+
+export enum PopoverButtonIcon {
+	"DropdownArrow" = "DropdownArrow",
+	"VerticalEllipsis" = "VerticalEllipsis",
+}
+
+export default defineComponent({
+	components: {
+		FloatingMenu,
+		IconButton,
+	},
+	props: {
+		action: { type: Function, required: false },
+		icon: { type: String, default: PopoverButtonIcon.DropdownArrow },
+	},
+	methods: {
+		handleClick() {
+			(this.$refs.floatingMenu as typeof FloatingMenu).setOpen();
+
+			if (this.action) this.action();
+		},
+	},
+	data() {
+		return {
+			MenuDirection,
+			MenuType,
+		};
+	},
+});
+</script>