Integrity check of the cryptography code provided by IDM Clients

## Description

A valid [concern](https://github.com/ipfs-shipyard/pm-idm/pull/35#discussion_r255601390) was raised about cryptography being done by IDM Clients, which will be available in the form of SDKs for different languages. There should be a recommendation regarding integrity checks, such as checksums or similar mechanisms, to ensure that the IDM Client that DApp developers include were not tampered.

For the IDM Client for the Web, we may use https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity.

## Acceptance Criteria

- [ ] Create one or two paragraphs with recommendations about this topic in the IDM Concept paper