docs(langchain): update with full support and add tool calling guide … (#1419)

* docs(langchain): update with full support and add tool calling guide with examples

* minor edits (#1424)

* Update docs/user-guides/langchain/runnable-rails.md

rm question

Signed-off-by: Miyoung Choi <[email protected]>

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Signed-off-by: Miyoung Choi <[email protected]>
Co-authored-by: Miyoung Choi <[email protected]>

Author: 2 people