Add 2.0.0 release docs

This MR requires oniro!372 (merged). While this is not merged, CI will fail.

requested review from @lucamiotto, @dricci783, @stefanschmidt, @mrybczyn, and @ektor5

assigned to @agherzan

requested review from @lucafavaretto

changed the description

added 1 commit

• e86a64e8 - Add 2.0.0 release notes

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added 2 commits

• 5a6277d1 - security: Create document tag for the security guide
• 6e3e6558 - Add 2.0.0 release notes

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Thanks, @mrybczyn. I've addressed all your comments.

requested review from @alpianon and @cpiana

I've added @alpianon @cpiana for review on the legal parts of the release notes. Looking forward to your feedback.