exa docs and python package update (#31307)

Added support for new Exa API features. Updated Exa docs and python
package (langchain-exa).

Description

Added support for new Exa API features in the langchain-exa package:
- Added max_characters option for text content
- Added support for summary and custom summary prompts
- Added livecrawl option with "always", "fallback", "never" settings
- Added "auto" option for search type
- Updated documentation and tests

Dependencies
- No new dependencies required. Using existing features from exa-py.

twitter: @theishangoswami

---------

Co-authored-by: Chester Curme <chester.curme@gmail.com>

libs/partners/exa/pyproject.toml

@@ -6,9 +6,9 @@ build-backend = "pdm.backend"
 authors = []
 license = { text = "MIT" }
 requires-python = ">=3.9"
-dependencies = ["langchain-core<1.0.0,>=0.3.15", "exa-py<2.0.0,>=1.0.8"]
+dependencies = ["langchain-core<1.0.0,>=0.3.60", "exa-py<2.0.0,>=1.0.8"]
 name = "langchain-exa"
-version = "0.2.1"
+version = "0.3.0"
 description = "An integration package connecting Exa and LangChain"
 readme = "README.md"