[graphiql] user-facing setting for persisting headers

[thomasheyenbrock]

The GraphiQL currently provides a prop shouldPersistHeaders that implementors can use to decide if header values should be persisted in localStorage. By default, no headers are persisted as a security measure (header values often times contain sensitive tokens). This defaults leads to many GraphiQL implementations that are not persisting headers.

As a GraphiQL user I would like to override this setting. I want to be able to choose if I want my headers to be persisted or not.

Proposal: Add a section to the settings dialog where users can override the default behavior of the GraphiQL implementation around persisting headers. This setting should only have effect if the shouldPersistHeaders prop is not set, or in other words, the GraphiQL implementation should still be able to explicitly enforce a choice about persisting headers and GraphiQL users can only choose their preference if the implementation is not explicit about this setting.

[TheMightyPenguin]

Gonna give this one a shot 👀

[TheMightyPenguin]

Found an accessibility issue when working on this one #2891