Reopen the last DM that was open when navigating back to chat (#81)

#60

Co-authored-by: mplorentz <mplorentz@users.noreply.github.com>
Reviewed-on: coracle/flotilla#81
Co-authored-by: Matt Lorentz <mplorentz@noreply.coracle.social>
Co-committed-by: Matt Lorentz <mplorentz@noreply.coracle.social>

src/app/util/history.ts

@@ -1,10 +1,14 @@
 import {page} from "$app/stores"
 
 export const lastPageBySpaceUrl = new Map<string, string>()
+export let lastChatUrl: string | undefined = undefined
 
 export const setupHistory = () =>
   page.subscribe($page => {
     if ($page.params.relay) {
       lastPageBySpaceUrl.set($page.params.relay, $page.url.pathname)
     }
+    if ($page.params.chat) {
+      lastChatUrl = $page.url.pathname
+    }
   })