Add Mullvad branding to NSIS installer

We may run into this reproducibility issue: tor-browser-build#29185 (closed)

It seems like the image encoder may or may not be reproducible depending on the icon.

added Feature label

marked this issue as related to #7 (closed)

changed the description

added Next Q1 labels

added Sponsor 131 label

marked this issue as related to #3 (closed)

removed the relation with #3 (closed)

marked this issue as related to #11 (closed)

added Windows label

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assigned to @pierov

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added Doing label

marked this issue as related to tor-browser-build#40742 (closed)

Not sure whether to close this or keep it in Backlog.

We're only missing the icon, but we have #11 (closed) for it.

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