Initial commit with files

Still need to fix the imports

src/lib/components/disclosure/DisclosureButton.svelte

@@ -0,0 +1,103 @@
+<script lang="ts">
+    import {
+        useDisclosureContext,
+        DisclosureStates,
+    } from "./Disclosure.svelte";
+    import { usePanelContext } from "./DisclosurePanel.svelte";
+    import { useId } from "./use-id";
+    import { Keys } from "./keyboard";
+    export let disabled = false;
+    const api = useDisclosureContext("DisclosureButton");
+    const panelContext = usePanelContext();
+    const id = `headlessui-disclosure-button-${useId()}`;
+
+    $: buttonStore = $api?.buttonStore;
+    $: panelStore = $api?.panelStore;
+
+    $: isWithinPanel =
+        panelContext === null ? false : panelContext === $api?.panelId;
+
+    function handleClick() {
+        if (disabled) return;
+
+        if (isWithinPanel) {
+            $api.toggleDisclosure();
+            $buttonStore?.focus();
+        } else {
+            $api.toggleDisclosure();
+        }
+    }
+
+    function handleKeyDown(event: KeyboardEvent) {
+        if (disabled) return;
+
+        if (isWithinPanel) {
+            switch (event.key) {
+                case Keys.Space:
+                case Keys.Enter:
+                    event.preventDefault();
+                    event.stopPropagation();
+                    $api.toggleDisclosure();
+                    $buttonStore?.focus();
+                    break;
+            }
+        } else {
+            switch (event.key) {
+                case Keys.Space:
+                case Keys.Enter:
+                    event.preventDefault();
+                    event.stopPropagation();
+                    $api.toggleDisclosure();
+                    break;
+            }
+        }
+    }
+
+    function handleKeyUp(event: KeyboardEvent) {
+        switch (event.key) {
+            case Keys.Space:
+                // Required for firefox, event.preventDefault() in handleKeyDown for
+                // the Space key doesn't cancel the handleKeyUp, which in turn
+                // triggers a *click*.
+                event.preventDefault();
+                break;
+        }
+    }
+
+    $: propsWeControl = isWithinPanel
+        ? {}
+        : {
+              id,
+              "aria-expanded": disabled
+                  ? undefined
+                  : $api.disclosureState === DisclosureStates.Open,
+              "aria-controls": $panelStore ? $api?.panelId : undefined,
+              disabled: disabled ? true : undefined,
+          };
+</script>
+
+{#if isWithinPanel}
+    <button
+        {...{ ...$$restProps, ...propsWeControl }}
+        on:click={handleClick}
+        on:keydown={handleKeyDown}
+    >
+        <slot
+            open={$api?.disclosureState === DisclosureStates.Open}
+            close={$api?.close}
+        />
+    </button>
+{:else}
+    <button
+        {...{ ...$$restProps, ...propsWeControl }}
+        bind:this={$buttonStore}
+        on:click={handleClick}
+        on:keydown={handleKeyDown}
+        on:keyup={handleKeyUp}
+    >
+        <slot
+            open={$api?.disclosureState === DisclosureStates.Open}
+            close={$api?.close}
+        />
+    </button>
+{/if}