v0.2.2: Sync with upstream

Tracks v0.1.10 ➡️ v0.2.1 from upstream. upstream's diff

Related releases:

• https://github.com/nanoporetech/jmespath-ts/releases/tag/v0.2.0
• https://github.com/nanoporetech/jmespath-ts/releases/tag/v0.2.1

Given that Deno doesn't need any toolchain configuration, the main benefits that are inherited are better types and code:

• Review types
• Split tests of extensions to spec into own module
• prefer builtin trimLeft method

v0.2.1: Allow root reference, More flexible custom functions

Tracks v0.1.5 to v0.1.10 from upstream.

• Access root JSONValue using $ symbol
• Specify optional arguments for custom functions
• Allow optional variadic arguments
• Fix type checking for optional arguments

v0.2.0: Initial release for Deno

Compared the upstream, AST types are largely redone to reduce casting and unsafe code.