* Add docs on how/when to use callbacks
* Update "create custom handler" section
* Update hierarchy
* Update constructor for BaseChain to allow receiving an object with args, rather than positional args
Doing this in a backwards compat way, ie. still supporting old positional args
* Remove requirement to implement serialize method in subcalsses of BaseChain to make it easier to subclass (until we work more on serialization)
* Fix code block api docs section for renamed imports
* Add docs and examples on creating custom chains, small reorg to chain docs
* Split callbacks docs into multiple pages, add docs on using callbacks in subclasses
* Fix broken links
* Fix one more
* Fix tsc transpiling issue
TSC was defining this property before the `super` call
* Lint
* Add example of __run
* Update
* Typo
- Loader lists all langchain objects used in the example, and finds the path to its reference docs
- CodeBlock component renders a card containing links to the reference doc of each
Nuno Campos