Add initial support for Notion filters

[scordio]

See #12.

This adds a DSL for Notion filters and the entry points for the following filter conditions:

Type-Specific Conditions

Checkbox

where().checkbox("Read").isEqualTo(true)

Multi-select

where().multiSelect("Author").contains("Lee Vinsel")
  .or().multiSelect("Author").contains("Megan Greenwell")

Note: the DSL is more verbose than the UI screen due to the Notion API's lack of support for multiple values.

Number

where().number("Pages").isGreaterThanOrEqualTo(42)

Select

where().select("Score /5").isEqualTo(⭐️⭐️⭐️)
  .or().select("Score /5").isEqualTo(⭐️⭐️)

Note: the DSL is more verbose than the UI screen due to the Notion API's lack of support for multiple values.

Compound Conditions

where().checkbox("Read").isEqualTo(true)
  .and(where().multiSelect("Author").contains("Kara Swisher").or().select("Score /5").isEqualTo(⭐️))