Add type definitions from @types/sql.js

Add `offsets(vtable, colIdx)` FTS5 auxilliary function.

Modeled after FTS3/4 `offsets` function, but targeting phrases instead
of terms. Implementation largely lifted from the FTS5 `highlights`
implementation, including some verbatim code that was not exported.

SQLite 3.38

emscripten 3.1.20
add aggregate functions

sqlite 3.38.5, size optimizations, more recent compiler

update sqlite

build with latest emscripten

bigint support and bug fixes

SQLite 3.35.0

 Add db.iterateStatements (sql-js#429)

 db.iterateStatements allows giving sql.js an SQL string and iterating over statements objects created from that string