Bumps `@version` in `mix.exs` and the compiler's second carrier,
`@compiler_version` in `lib/statifier_blocks/compiler.ex`, to 0.25.0,
and the README install pin to `~> 0.25`. The compiler version moves on
every release because it is stamped into every compilation record; no
compiled chart bytes move in this one.

Promotes the eleven `changelog.d/` fragments into a `## [0.25.0]`
section dated with the local date, grouped by heading and in
fragment-name order within each, and deletes them: sb-0buo, sb-543g,
sb-5xqr, sb-e491, sb-gbxt, sb-hgxl, sb-mcs8, sb-pgis, sb-qxyh, sb-uw3a,
sb-xio9. Every bullet is carried over byte for byte, including the
non-standard `Note` heading sb-5xqr wrote, carried last. Two bullets are
added under `Changed` for user-visible facts no fragment stated, both
checked against the code: `from_modules/2`'s new duplicate-`order`
raise, and `manifest/1` answering `nil` where it used to raise.

A minor: composites - `use StatifierBlocks.Composite` and
`Composite.Data`, `{module, state}` palette entries behind
`Palette.call/4`, expansion at Resolve with findings attributed one
level up, the editor's "Replace with its steps", `Recipe.members/2` and
the delete path that offers the arrangement, the `ViewModel` and
`Edit.Session` promotions, `selected_id`, `field_candidates` on path and
expression fields, and a `debounce` attr on the config form.

Fills the README for what a host needs: a composite declaration section
under "Registering your own block types", the Expand gesture, and four
rows the assigns table had drifted on - `selected_id`, `profile`,
`field_candidates` and `debounce`. Drops the "Not yet" fixtures-pane
bullet, which the drawer's Fixtures tab has falsified, for the two edges
this release deliberately leaves.

Refs: sb-ka9n