Fix: Replace /sw/check to /sw/img in service worker checkCache (#748)

# PR Checklist
- [ ] Have you checked if it works normally in all models? *Ignore this
if it doesn't use models.*
- [ ] Have you checked if it works normally in all web, local, and node
hosted versions? If it doesn't, have you blocked it in those versions?
- [ ] Have you added type definitions?

# Description
Currently, a specific endpoint that calls /sw/check in the service
worker checks whether '/sw/check' is cached.
Since the service worker does not have any logic to cache /sw/check
itself, the service worker will always respond that there is no cached
data.
This forces all data to be re-registered when getFileSrc is called from
globalApi.svelte.ts, and bots with a lot of assets will re-register all
data, which slows down bot changes.
Since I am not familiar with the internal structure of RisuAI, I have
temporarily modified the code to check /sw/img when the service worker
checks /sw/check.

public/sw.js

@@ -87,6 +87,13 @@ self.addEventListener('fetch', (event) => {
 async function checkCache(url){
     const cache = await caches.open('risuCache')
 
+    if(url.pathname.startsWith("/sw/check")) {
+        url.pathname = "/sw/img" + url.pathname.slice(9);
+        return new Response(JSON.stringify({
+            "able": !!(await cache.match(url))
+        }))
+    }
+
     return new Response(JSON.stringify({
         "able": !!(await cache.match(url))
     }))