Add a configuration for default tray width.

Adds a setting for the dialog tray default width.

requested review from @justin2pin

added 4 commits

• e213dadb...77c125a5 - 2 commits from branch project:2.1.x
• 141125a6 - Merge branch '2.1.x' into 3403159-sidebar-width
• 75a8259b - Add tray setting and update JS.

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added 1 commit

• 81cb6d5e - Build assets.

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added 1 commit

• d7a8d35f - Build assets again.

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added 1 commit

• c2798928 - Let the dialog inherit the saved width.

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merged