Move changes from exp2 to main

This is largely a move to simplify a lot of the readers
Also further breaks out functions.

internal/decompress/lz4.go

@@ -0,0 +1,13 @@
+package decompress
+
+import (
+	"io"
+
+	"github.com/pierrec/lz4/v4"
+)
+
+type Lz4 struct{}
+
+func (l Lz4) Reader(r io.Reader) (io.ReadCloser, error) {
+	return io.NopCloser(lz4.NewReader(r)), nil
+}