feat: add custom CEF V8 extensions support (#17)

* feat: Register extensions in render process

- Add CefExtensions type to hold V8 extension code
- Pass extensions through BrowserProcessAppBuilder
- Register extensions in RenderProcessHandler on WebKit initialization
- Decode JSON extensions from command line switch
- Prefix extension names with "v8/" per CEF convention
- Include actual JSON in error messages for debugging

l

* feat: refactor window.cef API and register as CEF extension

* fix: remove debug print statements in render process handler

* refactor: centralize EXTENSIONS_SWITCH constant in util.rs

* fmt

* refactor: implement Default trait for CefApiHandler

* docs: add documentation for CefApiHandler and its JavaScript API functions

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Co-authored-by: not-elm <elmgameinfo@gmail.com>

assets/js_emit.html

@@ -17,7 +17,7 @@
     let count = 0;
     window.setInterval(() => {
         console.log("Emitting count:", count);
-        window.cef.emit({
+        cef.emit({
             count,
         });
         countElement.innerText = count;