feat: support file and image attachments (#98)

* upload & view attachments to particles

* allow download of attachments

js/src/lib/firestore-particles.ts

@@ -4,6 +4,7 @@ import {
   onSnapshot,
   addDoc,
   getDoc,
+  getDocs,
   updateDoc,
   query,
   orderBy,
@@ -126,6 +127,19 @@ export async function getParticle(docPath: string): Promise<Particle | null> {
   return doc.data();
 }
 
+export async function getParticleChildren(
+  collectionPath: string,
+  orderByField: string = "created_at",
+  orderDirection: "asc" | "desc" = "asc",
+): Promise<Particle[]> {
+  const q = query(
+    typedCollection(collectionPath),
+    orderBy(orderByField, orderDirection),
+  );
+  const snap = await getDocs(q);
+  return snap.docs.map((d) => d.data());
+}
+
 export function subscribeToParticleChildren(
   collectionPath: string,
   onData: (children: Particle[]) => void,