v91.1

What's Changed

This release addresses Thunderbird 91 ESR.

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Added

• Enforce mail.suppress_content_language preference (see #19)
• Enforce mail.sanitize_date_header preference (see #19)
• Mention mail.compose.other.header preference (see #19)
• Note that an empty User-Agent may break Microsoft Exchange OAuth2 for non-RFP (see #19)

Changed

• Bump actions/checkout and actions/setup-node to v3

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Thanks to @giving-sesame for their suggestions !