RFR: 7832: Refresh dev guide

Tue Jun 28 14:35:17 UTC 2022

On Tue, 28 Jun 2022 08:12:19 GMT, Brice Dutheil <duke at openjdk.org> wrote:

> **Changes**
> * Update the style of interface navigation for easier readability (like _Preferences | Java ..._).
> * Mentioned the compiler language level, Eclipse may default to a higher level like 17 and results in IAE (`Unsupported class file major version` / `Incompatible class version`)
> * I believe the minimum version needed is now 2021-06 ?

Marked as reviewed by hirt (Lead).

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PR: https://git.openjdk.org/jmc/pull/404