Add CHANGELOG for 1.5.5

[philippjfr]

This release fixes a regression causing .node_modules to be bundled into our released wheel and introduces a number of bug fixes and enhancements. Many thanks to @mayonnaisecolouredbenz7, @pmeier, @Italirz, @Coderambling and our maintainer team @MarcSkovMadsen, @hoxbro, @ahuang11, @thuydotm, @maximlt and @philippjfr.

Enhancements

• Add ability to scroll_to a particular object on Column (#7206)
• Add pointer when hovering on Markdown copy button (#7490)
• Allow streaming to ChatStep (#7520)
• Improve ChatMessage repr (#7521)
• Add ChatInterface button tooltips (#7552)

Bug fixes

• Ensure FileDownload label text updates correctly (#7489)
• Fix Tabulator aggregation behavior (#7450)
• Fix typing for .servable method (#7530)
• Ensure NestedSelect respects disabled parameter (#7533)
• Ensure errors in hooks aren't masked by fallback to different signature (#7502)

Documentation

• Improve hold how-to guide (#7487, #7500)

Maintenance

• Enable strict type checking (#7497)
• Ensure node_modules aren't bundled into package (#7526)
• Internal cleanup of compatibility code for older param versions (#7527)

Compatibility

• Compatibility for websockets 14 when running on FastAPI server (#7491)
• Compatibility with Textual 0.86 (#7501)
• Compatibility with Altair 5.5.0 (#7523)
• Bump Vizzu version to 0.15 (#7485)