Add v10 upgrading doc

upgrading_notes/10.0.0.md

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+# Upgrading to 10.0.0
+
+## Internal technical rewrites
+
+Lots of the internal workings of cucumber have been refactored to use newer ruby syntaxes e.t.c.
+
+Because many of these files have been untouched in years it could be that there is some unexpected side-effects
+but it is expected that given the changes were all made to deeply internal files, there shouldn't be any
+issues
+
+## Deprecated Assistance / Cleanup helper methods
+
+### #text?
+
+The `#text?` method for checking differences in multi-line heredocs or texts has been slated for removal
+
+Should you wish to check multi-line text fragments for differences and issues, there are a host of better-suited
+libraries that handle this better, and this should be handled outside the remit of cucumber
+
+### Cucumber.use_legacy_autoloader configuration setting
+
+This was intended as a stop-gap after version3->4 had a lot of new architectural changes
+
+It was only ever meant to live in cucumber for a short while, but given we never got around to removing it, now
+is as good a time as any to deprecate it (It will be deleted and won't return from v11)
+
+### StepDefinitionLight
+
+This class and its associated actions is now considered deprecated. It serves little to no purpose other than in
+one of the legacy formatters that we aim to remove and port to messages and some associated "shim" languages
+which aren't in the purview of the team any more
+
+## Removed Assistance / Cleanup helper methods
+
+### CCK
+
+The CCK previously used to duplicate some assets during testing - This is now removed and the assets that are used
+are now purely from the CCK proper. This is the final step in full conformance for the CCK
+
+### Tag Expressions Sanitization helpers
+
+This is again another item that should have been removed a long time ago, there is both some internal `aruba` helpers
+and some external facing helpers that will attempt to fix poor tag expression syntax
+
+In all situations now anything that is not a valid tag expression will simply crash and the user will need to fix
+up their code to be syntactically valid
+
+### StepDefinitionLight associated helpers
+
+The associated helpers or secondary usages from this "now deprecated" class are now removed
+
+Nothing related to this should be used going forwards - the entire area of the codebase supporting this will
+be completely deleted in v11
+
+### Webrick alias handlers
+
+There is a lot of legacy code regarding some tests that needed webrick handlers. Many of these tests have been
+modified and we are going to slowly phase out the tests that "check" or "validate" other frameworks
+
+The reason for the above is this is an inverse relationship. Said frameworks should be using cucumber to validate
+their usage, not the other way around - as if we found an issue, we would do nothing more than bubble it up to
+the relevant repository