Bumps `@version` in `mix.exs` and the compiler's second carrier,
`@compiler_version` in `lib/statifier_blocks/compiler.ex`, to 0.22.0,
and the README install pin to `~> 0.22`. The compiler version moves
because this release changes compiled bytes for three kinds of
document, which the changelog's second paragraph names.

Promotes the five `changelog.d/` fragments into a `## [0.22.0]`
section dated with the local date, grouped by heading and in
fragment-name order within each, and deletes them: sb-0na2, sb-cjou,
sb-hgjk, sb-hxs5, sb-y4i7. Every bullet is carried over byte for
byte; the lead paragraphs are the only prose written here.

A minor with notes: the failure classing across the vocabulary, the
`core.on_event` payload declaration and its capture refusal, dotted
`collect` paths, the editor's `compile_options` assign, and the
`statifier_datamodel` floor at `~> 0.3`.

Refs: sb-n7sn