allow texture streaming(png, jpeg for now) and use texture url instead of passing textures in base64

Cargo.lock

@@ -978,13 +978,13 @@ name = "open_tavern"
 version = "0.1.0"
 dependencies = [
  "axum",
- "base64",
  "futures-util",
  "serde",
  "serde_json",
  "sqlx",
  "tavern_macros",
  "tokio",
+ "tokio-util",
 ]
 
 [[package]]
@@ -1751,6 +1751,19 @@ dependencies = [
  "tungstenite",
 ]
 
+[[package]]
+name = "tokio-util"
+version = "0.7.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "66a539a9ad6d5d281510d5bd368c973d636c02dbf8a67300bfb6b950696ad7df"
+dependencies = [
+ "bytes",
+ "futures-core",
+ "futures-sink",
+ "pin-project-lite",
+ "tokio",
+]
+
 [[package]]
 name = "tower"
 version = "0.4.13"