[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/util/osutil/osfs.go

@@ -0,0 +1,33 @@
+package osutil
+
+import (
+	"io/fs"
+	"os"
+)
+
+// FS implements [fs.FS], [fs.StatFS], and [fs.ReadFileFS]
+// using package [os].
+//
+// This filesystem does not respect [fs.ValidPath] rules,
+// and fails [testing/fstest.TestFS]!
+//
+// Still, it can be a useful tool to unify implementations
+// that can access either the [os] filesystem or an [fs.FS].
+// It's OK to use this to open files, but you should avoid
+// opening directories, resolving paths, or walking the file system.
+type FS struct{}
+
+// Open implements [fs.FS].
+func (FS) Open(name string) (fs.File, error) {
+	return OpenFile(name, os.O_RDONLY, 0)
+}
+
+// ReadFileFS implements [fs.StatFS].
+func (FS) Stat(name string) (fs.FileInfo, error) {
+	return os.Stat(name)
+}
+
+// ReadFile implements [fs.ReadFileFS].
+func (FS) ReadFile(name string) ([]byte, error) {
+	return os.ReadFile(name)
+}