243: Update docs-gen to use pekko-sbt-paradox extension (#27)

* 243: Update docs-gen to pekko-sbt-paradox

Change akka -> Pekko in filenames
Import pekko-sbt-paradox extension
Minimal changes to pekkosampleplugin to accommodate this

* Markups: Run scalafmt

* #243: markups: final replacements of akka in docs

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Co-authored-by: sb5 <sb5@ad.datcon.co.uk>
15 files changed