Cai-causal-graph

- Fixed a bug in `cai_causal_graph.identify_utils.identify_instruments` and
`cai_causal_graph.identify_utils.identify_mediators`, where an unclear error was raised if the `source` node was a
descendant of the `destination` node. Instead, these methods now return an empty list in that case.
- Extended the quickstart documentation to describe how to set the `variable_type` when adding a
`cai_causal_graph.graph_components.Node` / `cai_causal_graph.graph_components.TimeSeriesNode` to a
`cai_causal_graph.causal_graph.CausalGraph` / `cai_causal_graph.time_series_causal_graph.TimeSeriesCausalGraph`,
respectively.

- Improved documentation.

- Fixed a bug for forward extension in the
`cai_causal_graph.time_series_causal_graph.TimeSeriesCausalGraph.extend_graph` method in
`cai_causal_graph.time_series_causal_graph.TimeSeriesCausalGraph`.

> **_NOTE:_** **Backwards compatibility warning!** The definition of the
> `cai_causal_graph.type_definitions.EdgeConstraint` enumeration has changed.

- Updated the `cai_causal_graph.type_definitions.EdgeConstraint` enumeration to simplify the enumeration members and
exposed it at the root level, so it can be imported as `from cai_causal_graph import EdgeConstraint`.
`cai_causal_graph.type_definitions.EdgeConstraint` is not used by the `cai-causal-graph` package but any packages
that rely on its definition, must be updated to reflect the new members.

- Fixed the docstrings of `cai_causal_graph.time_series_causal_graph.TimeSeriesCausalGraph.from_adjacency_matrices`,
such that the examples render properly.

- Fixed a bug where `cai_causal_graph.utils.get_variable_name_and_lag` would not match variable names with
non-alphanumeric characters, and would not match variable names with the string `lag` or `future` in them.