Release B-tree version 2.0.0-alpha.11.
Release B-tree version 2.0.0-alpha.11.

 * Implement a common write collection. Closes #591.
 * Add link to last commit message to diary.
 * Restore extractor. Closes #590.
 * Is is faster to skip the promise?
 * How much slower is `BigInt`?
 * Tidy operation id wrap.
 * Simplify `Cursor.flush`.

Closes #592.

bigeasy/strata,bigeasy/strata