Release mp4forge 0.5.0

[bakgio]

Summary

Prepare the mp4forge 0.5.0 release.

What changed

• bump the crate version to 0.5.0
• update the README dependency snippets to the new release version
• update the bug-report template placeholder to the new release version
• add a new top changelog entry summarizing the work included since 0.4.0

Release highlights

• first-class encrypted metadata support, including typed senc, typed sgpd(seig), resolved sample-encryption helpers, and broader encrypted fragmented coverage
• additive top-level sidx analysis, planning, and rewrite support for supported fragmented layouts
• broad typed-box expansion across metadata, fragmented timing, codec, and legacy payload families
• stronger low-level robustness for legal trailing-byte VisualSampleEntry layouts
• additive prft timing and flag helpers plus wider regression coverage