Enable customisation of QR Code font

[luke-jr]

May need the fixes in #506 to work cleanly in all cases, but should still be a net improvement on its own

[DrahtBot]

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Concept ACK	hebasto

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[hebasto]

Concept ACK on adding a new customization option for the QR code font.

Lightly tested b14c9d0. It seems to work as expected.

However, I think that QR image widget must consider the font size for adjusting its own size. Otherwise, the image can be unreadable and confusing for the user:

The second commit modifies the code introduced in the first one. Therefore, please squash them.

[DrahtBot]

🤔 There hasn't been much activity lately and the CI seems to be failing.

If no one reviewed the current pull request by commit hash, a rebase can be considered. While the CI failure may be a false positive, the CI hasn't been running for some time, so there may be a real issue hiding as well. A rebase triggers the latest CI and makes sure that no silent merge conflicts have snuck in.