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/lz4.go

@@ -0,0 +1,15 @@
+package decompress
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/pierrec/lz4/v4"
+)
+
+type Lz4 struct{}
+
+func (l Lz4) Decompress(data []byte) ([]byte, error) {
+	rdr := lz4.NewReader(bytes.NewReader(data))
+	return io.ReadAll(rdr)
+}