Add brush size settings and shortcuts

[MichaelBuessemeyer]

This PR adds a second keyboard shortcut to volume tracing to increase/decrease the brush size. It also added it to the settings in the settings tab on the left side.

URL of deployed dev instance (used for testing):

• https://addbrushsizesettingsandshortcuts.webknossos.xyz

Steps to test:

• open volume tracing and select the brush mode
• the brush should resize according to the settings set on the left tab, and according to the shortcuts (shift + mouse wheel/ shift + i,o)
• the settings option for the brush size should only appear in volume tracing

Issues:

• fixes Add brush size to settings and add brush size shortcuts #2328

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• Updated changelog
• Ready for review

[normanrz]

looks good 👍

[normanrz]

Typo Brush Size

[philippotto]

Nice 👍 Can you comment here that you implemented this, @MichaelBuessemeyer? https://discuss.webknossos.org/t/brush-size-in-volume-mode/285/12

In the cases, where we know who exactly wished for a specific feature (i.e., when there is a discuss link in the gh issue), we usually let them directly know about it, since not everybody looks through the changelog regularly :)