feat: implements text/event-stream(SSE) MIME parser (#1416)

Co-authored-by: 007gzs <007gzs@gmail.com>

plugins/wasm-rust/example/sse-timing/README.md

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+## Proxy-Wasm plugin example: SSE Timing
+
+Proxy-Wasm plugin that traces Server-Side Event(SSE) duration from request start.
+
+### Building
+
+```sh
+$ make
+```
+
+### Using in Envoy
+
+This example can be run with [`docker compose`](https://docs.docker.com/compose/install/)
+and has a matching Envoy configuration.
+
+```sh
+$ docker compose up
+```
+
+#### Access granted.
+
+Send HTTP request to `localhost:10000/`:
+
+```sh
+$ curl localhost:10000/
+```