* Synchronise package with module template (July 2023)

* Update pull request template

* Update coverage

…103)

This reverts commit ab0ebca.

As #98 removes the ability to import or require from paths like
 `@metamask/rpc-errors/dist/foo` and a release is still pending for the
 current major, this will have to be temporarily reverted.

* types: Make Data type-parameter optional in JsonRpcError

This is in order to provide backwards-compatibility with code
implemented towards v5.0.0.

* fix/types: make cause actually optional in DataWithOptionalCause

* deps: @metamask/utils@^5.0.0->^8.0.0

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Co-authored-by: legobt <6wbvkn0j@anonaddy.me>