I standardised no_std errors to be Display + Debug, which is closer to the "real" std::error::Error trait (and is what serde does too for no_std), exposed a couple of helpers to make constructing them from strings simpler (scale-value and subxt use these) and made use of derive_more since it's used in scale-value anyway, and is rather helpful.

Also bumped the version ready for a new release once this merges.

Part of a series:

• You are here: Improve error handling + consistency when no_std #31
• Improve error handling + consistency when no_std scale-encode#13
• Bump scale-encode and scale-decode scale-value#40

Changes tested against Subxt; I'll update that next.