Add configurable theme colours to filesystem

svelte/src/layout/HelpButton.svelte

@@ -0,0 +1,20 @@
+<script>
+export let toggle = false;
+</script>
+
+<button class="button small_button round"
+	class:button_highlight={toggle}
+	style="margin: 0;"
+	on:click={() => toggle = !toggle}
+>
+	<i class="icon">help</i>
+</button>
+
+<style>
+.button {
+	flex: 0 0 content;
+	background: none;
+	color: var(--body_text_color);
+	box-shadow: none;
+}
+</style>