Documentation for breaking changes of Secure Cadence

[turbolent]

Issue To Be Solved

Given that the release of Secure Cadence is imminent, we should update the documentation to reflect the future behaviour.

Suggested Solution

In particular, we should update the documentation to reflect the following breaking changes:

• Zero-pad string representation of addresses #1214 @turbolent
• Use common super-type for expression type inferring #1027 @SupunS
• Taking a reference to an optional value now produces an optionally-typed reference #1303 @dsainati1
• Disallow arithmetic, comparison and bitwise operations on number supertypes #1360 @SupunS

We can mostly just copy-and-paste the new behaviour from the breaking changes announcement in the forum.

We should maybe wait with merging related PRs until the sporks are closer.

[SupunS]

Type inferring doc updates were already added in #1054

[turbolent]

@SupunS Ah, great! I only checked the PRs themselves, sorry for the ping