[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/sysfs/nonblock_unix.go

@@ -0,0 +1,17 @@
+//go:build !windows && !plan9 && !tinygo
+
+package sysfs
+
+import (
+	"syscall"
+
+	"github.com/tetratelabs/wazero/experimental/sys"
+)
+
+func setNonblock(fd uintptr, enable bool) sys.Errno {
+	return sys.UnwrapOSError(syscall.SetNonblock(int(fd), enable))
+}
+
+func isNonblock(f *osFile) bool {
+	return f.flag&sys.O_NONBLOCK == sys.O_NONBLOCK
+}