Increase nginx buffer sizes in dev

These larger buffer sizes accommodate larger requests that are often complained about in Valet support issues.
These updates are inspired by common configs in Homestead.

I've been using these in my local Valet config for 4+ months, without any negative side-effects.

Edit: commented-out several, and made consistent with Forge defaults

cli/stubs/valet.conf

@@ -31,3 +31,15 @@ server {
         deny all;
     }
 }
+
+
+## Size Limits & Buffer Overflows 
+## the size may be configured based on the needs. 
+client_body_buffer_size 100k;
+client_header_buffer_size 1k;
+large_client_header_buffers 2 1k;
+
+# large buffer support
+#proxy_buffer_size 4096k;
+#proxy_buffers 128 4096k;
+#proxy_busy_buffers_size 4096k;