[experiment] add alternative wasm sqlite3 implementation available via build-tag (#2863)

This allows for building GoToSocial with [SQLite transpiled to WASM](https://github.com/ncruces/go-sqlite3) and accessed through [Wazero](https://wazero.io/).

vendor/github.com/ncruces/go-sqlite3/driver/savepoint.go

@@ -0,0 +1,27 @@
+package driver
+
+import (
+	"database/sql"
+	"time"
+
+	"github.com/ncruces/go-sqlite3"
+)
+
+// Savepoint establishes a new transaction savepoint.
+//
+// https://sqlite.org/lang_savepoint.html
+func Savepoint(tx *sql.Tx) sqlite3.Savepoint {
+	var ctx saveptCtx
+	tx.ExecContext(&ctx, "")
+	return ctx.Savepoint
+}
+
+type saveptCtx struct{ sqlite3.Savepoint }
+
+func (*saveptCtx) Deadline() (deadline time.Time, ok bool) { return }
+
+func (*saveptCtx) Done() <-chan struct{} { return nil }
+
+func (*saveptCtx) Err() error { return nil }
+
+func (*saveptCtx) Value(key any) any { return nil }