- mix.exs: @version 0.19.0 -> 0.20.0
- lib/statifier_blocks/compiler.ex: @compiler_version to match
- README.md: install pin ~> 0.19 -> ~> 0.20
- CHANGELOG.md: assembles the 0.20.0 section from seven fragments
- changelog.d/: the seven promoted fragments deleted

A minor and not a patch, with two breaking edges the section names.
StatifierBlocks.Predicates.Datamodel is gone and its functions are
StatifierDatamodel.Index's under the same names, so a caller swaps the
module name and nothing else; and a type expression spelled exactly
"unknown" now reads as the permissive :unknown rather than as an opaque
expression that happens to be spelled that way, which only ever admits.
The rest is the typed environment: a path-to-type map at any position
carried by one pre-order walk, write signatures across core.*, and the
drawer's Datamodel tab.

Cut, not published: the tag, the GitHub release and the Hex publish are
the operator's. Dependency requirements resolve from Hex alone -
statifier_datamodel ~> 0.1 and the optional statifier_ui ~> 0.8 - and
mix hex.build accepts the package at this version.

Refs: sb-7gn7