[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/internal/util/mmap_other.go

@@ -0,0 +1,21 @@
+//go:build !(darwin || linux) || !(amd64 || arm64 || riscv64) || sqlite3_noshm || sqlite3_nosys
+
+package util
+
+import (
+	"context"
+
+	"github.com/tetratelabs/wazero/experimental"
+)
+
+type mmapState struct{}
+
+func withAllocator(ctx context.Context) context.Context {
+	return experimental.WithMemoryAllocator(ctx,
+		experimental.MemoryAllocatorFunc(func(cap, max uint64) experimental.LinearMemory {
+			if cap == max {
+				return virtualAlloc(cap, max)
+			}
+			return sliceAlloc(cap, max)
+		}))
+}