docs: add outline of betree and modules

docs: correct epsilon in overview

docs: add concept overview

docs: add traits for DML

docs: add b-epsilon tree overview

docs: add section about root tree

docs: add todo for julea-sys

docs: add segment and copy on write

docs/betree: add section about root tree

docs: create mdbook

docs/ci: add pages build & deploy workflow

docs/ci: fix event name typo

docs: move detailed info to submenu

docs: add docs build dir to gitignore

docs: add docs notice to readme

docs: specify site-url

docs: use prebuilt binary in publish

docs: add bectl chapter

docs: add julea-sys chapter

docs: add chapter julea-betree

docs: add intro

docs/ci: add graphviz

docs: add graphviz tree overview

docs: rework design chapter betree

docs: fix typo in apt pkg name

docs: Fix typos …

Co-authored-by: Michael Kuhn

docs: fix shell examples comments

docs: fix unclear sentences