Document electron main process integration sendOnCreate (#7639)

Co-authored-by: vivianyentran <20403606+vivianyentran@users.noreply.github.com>

Author: AbhiPrasad

src/platforms/javascript/guides/electron/configuration/integrations/default.mdx

@@ -226,6 +226,17 @@ Sentry.init({
 });
 ```
 
+The default behavior is to only send sessions on error or when the main process ends. To send sessions when the main process is created, enable the `sendOnCreate` option.
+
+```
+import * as Sentry from "@sentry/electron";
+
+Sentry.init({
+  dsn: "___PUBLIC_DSN___",
+  integrations: [new Sentry.Integrations.MainProcessSession({ sendOnCreate: true })]
+});
+```
+
 ## Renderer Process
 
 ### `ScopeToMain`