Feature: linkcheck-action (#534) (#542)

- Add support for local build and linkchecking of docs
- Add GitHub Action to automatically check links before prior to
publication
- Minor reformat of Contributing readme
- Fix existing broken links

Co-authored-by: Hunter Gerlach <hunter@huntergerlach.com>

Co-authored-by: Hunter Gerlach <HunterGerlach@users.noreply.github.com>
Co-authored-by: Hunter Gerlach <hunter@huntergerlach.com>

docs/modules/llms.rst

@@ -7,13 +7,13 @@ you can interact with a variety of LLMs.
 
 The following sections of documentation are provided:
 
-- `Getting Started <llms/getting_started.html>`_: An overview of all the functionality the LangChain LLM class provides.
+- `Getting Started <./llms/getting_started.html>`_: An overview of all the functionality the LangChain LLM class provides.
 
-- `Key Concepts <llms/key_concepts.html>`_: A conceptual guide going over the various concepts related to LLMs.
+- `Key Concepts <./llms/key_concepts.html>`_: A conceptual guide going over the various concepts related to LLMs.
 
-- `How-To Guides <llms/how_to_guides.html>`_: A collection of how-to guides. These highlight how to accomplish various objectives with our LLM class, as well as how to integrate with various LLM providers.
+- `How-To Guides <./llms/how_to_guides.html>`_: A collection of how-to guides. These highlight how to accomplish various objectives with our LLM class, as well as how to integrate with various LLM providers.
 
-- `Reference </reference/modules/llms.html>`_: API reference documentation for all LLM classes.
+- `Reference <../reference/modules/llms.html>`_: API reference documentation for all LLM classes.
 
 
 .. toctree::
@@ -21,7 +21,7 @@ The following sections of documentation are provided:
    :name: LLMs
    :hidden:
 
-   llms/key_concepts.md
-   llms/getting_started.ipynb
-   llms/how_to_guides.rst
-   Reference</reference/modules/llms.rst>
+   ./llms/key_concepts.md
+   ./llms/getting_started.ipynb
+   ./llms/how_to_guides.rst
+   Reference<../reference/modules/llms.rst>