XSLT compat data migration is being started and set up in #2026.

Changes that need to be made as part of this:

• Move all XSLT elements under the XSLT elements reference
• Rename /docs/Web/XSLT/Elements/* to /docs/Web/XSLT/Element/*
• Modernise XSLT macros (Modernize XSLT macros kumascript#734)

Pages which need conveting:

• XSLT/Element/apply-imports
• XSLT/Element/apply-templates
• XSLT/Element/attribute
• XSLT/Element/attribute-set
• XSLT/Element/call-template
• XSLT/Element/choose
• XSLT/Element/comment
• XSLT/Element/copy
• XSLT/Element/copy-of
• XSLT/Element/decimal-format
• XSLT/Element/element
• XSLT/Element/fallback
• XSLT/Element/for-each
• XSLT/Element/if
• XSLT/Element/import
• XSLT/Element/include
• XSLT/Element/key
• XSLT/Element/message
• XSLT/Element/namespace-alias
• XSLT/Element/number
• XSLT/Element/otherwise
• XSLT/Element/output
• XSLT/Element/param
• XSLT/Element/preserve-space
• XSLT/Element/processing-instruction
• XSLT/Element/sort
• XSLT/Element/strip-space
• XSLT/Element/stylesheet (Begin work on converting XSLT data #2026)
• XSLT/Element/template
• XSLT/Element/text
• XSLT/Element/transform
• XSLT/Element/value-of
• XSLT/Element/variable
• XSLT/Element/when
• XSLT/Element/with-param