Add GooseAI, CerebriumAI, Petals, ForefrontAI (#981)

Add GooseAI, CerebriumAI, Petals, ForefrontAI

docs/ecosystem/petals.md

@@ -0,0 +1,17 @@
+# Petals
+
+This page covers how to use the Petals ecosystem within LangChain.
+It is broken into two parts: installation and setup, and then references to specific Petals wrappers.
+
+## Installation and Setup
+- Install with `pip install petals`
+- Get an Huggingface api key and set it as an environment variable (`HUGGINGFACE_API_KEY`)
+
+## Wrappers
+
+### LLM
+
+There exists an Petals LLM wrapper, which you can access with 
+```python
+from langchain.llms import Petals
+```