Added custom themes, import/export option with json (#159)

Reviewed-on: https://codeberg.org/ArkHost/HelixNotes/pulls/159

src/lib/api.ts

@@ -1,6 +1,7 @@
 import { invoke } from "@tauri-apps/api/core";
 import type {
   AppConfig,
+  CustomTheme,
   NoteContent,
   NoteEntry,
   NoteMeta,
@@ -36,6 +37,22 @@ export async function setAccentColor(color: string): Promise<void> {
   return invoke("set_accent_color", { color });
 }
 
+export async function saveCustomTheme(theme: CustomTheme): Promise<void> {
+  return invoke("save_custom_theme", { theme });
+}
+
+export async function deleteCustomTheme(id: string): Promise<void> {
+  return invoke("delete_custom_theme", { id });
+}
+
+export async function exportCustomTheme(id: string, path: string): Promise<void> {
+  return invoke("export_custom_theme", { id, path });
+}
+
+export async function importCustomThemes(path: string): Promise<CustomTheme[]> {
+  return invoke("import_custom_themes", { path });
+}
+
 export async function setFontSize(size: number): Promise<void> {
   return invoke("set_font_size", { size });
 }