Update Modal App: (#1755)

* Update Modal App:

Updated Modal App to include:

1. Latest Modal API usage
2. Ability to launch different Pipecat pipelines, much like the
   simple chatbot example
3. Ability to choose which pipeline is launched via the
   /connect endpoint
4. Added a pipeline option for connecting to a self-hosted LLM
   on Modal
5. Improved READMEs
6. Added a web client for interacting with the Modal deployment

tmp

* Update README

examples/deployment/modal-example/server/env.example

@@ -0,0 +1,14 @@
+DAILY_API_KEY=
+
+# determines which bot file to default to: 'openai', 'gemini', or 'vllm'
+BOT_IMPLEMENTATION=openai
+
+# needed for the openai bot pipeline
+OPENAI_API_KEY=
+ELEVENLABS_API_KEY=
+
+# needed for the gemini live bot pipeline
+GOOGLE_API_KEY=
+
+# needed if you modified the API Key for your self-hosted LLM
+VLLM_API_KEY=