[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/tetratelabs/wazero/internal/expctxkeys/memory.go

@@ -0,0 +1,4 @@
+package expctxkeys
+
+// MemoryAllocatorKey is a context.Context key for the experimental memory allocator.
+type MemoryAllocatorKey struct{}