more validation tests for gemma video rendering

Adds 'doom like' 3dviprmaze-vip for demo (VERY VERY SLOW)
updates egui interface to let user select from files in resources/roms
updates cargo to centralize dependencies
95 passing tests

gemmatelnet/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "gemmatelnet"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+gemma = { path = "../gemma" }

gemmatelnet/src/bin/gemmatelnetd.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Taxation is Theft");
+}