doc(build): explanation on git submodules and refactor of sync script

• Explanation on the git submodule commands
• Refactor of scripts

added Documentation v2.0 labels

requested review from @arora

assigned to @defosseu

removed v2.0 label

added v1.5.1 label

added 1 commit

• e0eaa961 - doc(ci): fix typo

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added 1 commit

• 2e136d45 - doc(build): U20 is the base image for this release

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merged

mentioned in commit 90ee42f8