Add changelog to `:app-thunderbird`

<?xml version="1.0" encoding="utf-8"?>

<?xml-stylesheet type="text/xsl" href="changelog_style.xsl"?>

<!--

     The master change log is kept in res/raw/changelog_master.xml.

     Locale-specific versions are kept in res/raw-<locale qualifier>/changelog.xml.

-->

<changelog>

    <release version="0.1b1" versioncode="2" date="2024-09-25">

        <change>Initial build</change>

    </release>

</changelog>