Initial work

Create Reader
Pulled back in Inode decoding and superblock
New Data and Metadata readers
Added getting of id, fragment, and export table data lazily
Added README to squashfs/squashfs

internal/decompress/zstd.go

@@ -0,0 +1,19 @@
+package decompress
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/klauspost/compress/zstd"
+)
+
+type Zstd struct{}
+
+func (z Zstd) Decompress(data []byte) ([]byte, error) {
+	rdr, err := zstd.NewReader(bytes.NewReader(data))
+	if err != nil {
+		return nil, err
+	}
+	defer rdr.Close()
+	return io.ReadAll(rdr)
+}