docs: V24-V25 upgrade guide (DS) (#4679)

* docs: add DS sections

* chore: fix Value errors

* chore: merge theming sections

* add more details about how to upgrade TreeGrid

* explain how indexes are treated in flat and non-flat hierarchy format

* revert package.json

* apply proper styling to diff code blocks

* minor formatting fixes

* add HierarchicalCommunicationController to the list, minor polish

* minor wording polish

* mention hierarchy formats

* make Components a top level section

* Update articles/upgrading/index.adoc

Co-authored-by: Serhii Kulykov <[email protected]>

* Update articles/upgrading/index.adoc

Co-authored-by: Serhii Kulykov <[email protected]>

* Update articles/upgrading/index.adoc

Co-authored-by: Rolf Smeds <[email protected]>

* Update articles/upgrading/index.adoc

Co-authored-by: Rolf Smeds <[email protected]>

* sort sections alphabetically

* move Overlays under Components section

* remove mention of Tailwind

* fix heading level

* rework loading Lumo section

* improve overlays section

* add scrollToItem section

* remove CssImport alternative

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Co-authored-by: Sergey Vinogradov <[email protected]>
Co-authored-by: Serhii Kulykov <[email protected]>
Co-authored-by: Rolf Smeds <[email protected]>
Co-authored-by: Sascha Ißbrücker <[email protected]>
Co-authored-by: ugur-vaadin <[email protected]>

Author: 6 people