Subgrounds

Feature
* Export more symbols to `subgrounds` ([`3c59fe9`](https://github.com/0xPlaygrounds/subgrounds/commit/3c59fe9e0f96947d23905a0eab384c01cf8d42f7))

Documentation
* Add description about testing ([`f2231c2`](https://github.com/0xPlaygrounds/subgrounds/commit/f2231c2b02fe0194409b91d865dedd6d45ecd92c))
* Migrated `docs/` and clean up ([`9deca3b`](https://github.com/0xPlaygrounds/subgrounds/commit/9deca3bc48a38018c9baa73ba625ec37decf1670))
* Add CONTRIBUTING.md + README.md edits ([`2218d47`](https://github.com/0xPlaygrounds/subgrounds/commit/2218d47df13bf2cc5a43950f1106b62c20a16d5f))
* Trigger docs flow (removed some files) ([`1ee17e5`](https://github.com/0xPlaygrounds/subgrounds/commit/1ee17e5129192c3c202830f929f284c8ca019650))
* Simplify contributing cmds ([3](https://github.com/0xPlaygrounds/subgrounds/issues/3)) ([`0b4f3a2`](https://github.com/0xPlaygrounds/subgrounds/commit/0b4f3a2590a3e916e614bff97b578bb32d5097e2))

Fix
- Issue causing null object in `SyntheticField`s

Fix
- Update `SchemaMeta` to `Pydantic` model for extra validation

Fix
- Schema cache directory path
- `where` filter getting dropped during pagination

Description
This release overhauls how pagination is performed in Subgrounds.

BREAKING CHANGES
* The `auto_paginate` argument of toplevel querying functions has been replaced by the `pagination_strategy` argument (setting the latter to `None` disables pagination).

Feature
* Subgrounds users can now define and use their own pagination strategy (see Custom pagination strategy for more details).
* Users select the pagination strategies to use when calling toplevel querying functions:

py
df = sg.query_df(field_paths, pagination_strategy=MyPaginationStrategy)


* Subgrounds provides two pagination strategies out of the box:
* `LegacyStrategy` (the strategy used prior to this update)
* `ShallowStrategy`, which is much faster than `LegacyStrategy` in some cases, but does not support pagination on nested fields (see Available pagination strategies for more details).

Fix
* Fix bug that would cause a crash when calling one of the toplevel querying functions with only one `FieldPath` object (e.g.: `sg.query_df(pairs.id)`).

Feature
* Iterative versions of toplevel querying functions to allow developers to process queried data page by page when automatic pagination returns more than one page
* `query_df` -> `query_df_iter`
* `query` -> `query_iter`
* `query_json` -> `query_json_iter`
* `execute` -> `execute_iter`
* Add option to set subgraph schema cache directory in `load_subgraph` and `load_api`.
* Defaults to `./schemas/`
* Add useful `SyntheticField` helper `datetime_of_timestamp`
* `Subgrounds` class can now be imported from toplevel module: `from subgrounds import Subgrounds`
* Add `SyntheticField.datetime_of_timestamp` helper function to easily create a `SyntheticField` that converts a Unix timestamp into a human readable datetime string
* Add `SyntheticField.map` helper function to easily create a "map" `SyntheticField` from a dictionary

Fix
* Fix bug that caused some queries to fail with automatic pagination enabled

Chore
* Migrate package manager from `pipenv` to `poetry`
* Migrate docs from plain `sphinx` to `mudkip`
* Made `dash` an optional extra dependency.
* To use Subgrounds `dash` and `plotly` wrappers, run `pip install subgrounds[dash]`