Go lib for Data Segment Index

• Go implementation for reading and writing data segment index
• See https://github.com/filecoin-project/FIPs/blob/9a3bfe48e75bc6d34329df8653cb6f431efc967d/FRCs/frc-verifiable-data-aggregation.md#data-segment-index
• Produce index entries in Fr32 padded format based on inputs (CommDS, offset, length) computing the checksum
• Read index entries in Fr32 padded format, check their checksum
• Read the whole index from Fr32 padded format, find valid entries and output their content
• Take in an array of (CommDS, offset, length) tuples and produce an index in Fr32 padded format

Padding and unpadding: https://github.com/filecoin-project/lotus/blob/b706efc33bd392d5be4f0be6679f8c5b23d98e26/storage/sealer/fr32/fr32.go