Release v0.4.0-beta.6

What's Changed

• Add local Library authoring and publication CLI by @DamianReeves in #945
• feat: dogfood first V3 arity rule through native eval by @DamianReeves in #948
• Send typed CLI peer kind during MEP initialize by @DamianReeves in #954
• chore: pin frontends that accept the sources compile envelope by @DamianReeves in #955
• feat(cli): send every frontend the sources compile envelope by @DamianReeves in #956
• feat(ir): draft Amazon Ion IR format by @DamianReeves in #951
• fix(deps): update dependency gleam_stdlib to v1 by @renovate[bot] in #953
• chore: prepare v0.4.0-beta.6 release by @DamianReeves in #971

Full Changelog: v0.4.0-beta.5...v0.4.0-beta.6