Correct changelog format and spelling

• By opening this merge request, you agree to release your code and all other changes under the GPL 3 license and to abide by the terms set by this license.
• Migrations have been added if applicable (migrations are always necessary for removing/renaming item asset files)
• Significant changes of this merge request have been added to the changelog.

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Changelog

The format is based on Keep a Changelog.

Added

• Mention of completed Spanish translation in the changelog.

Changed

• Make all update sentences end with full stop in the changelog for consistency.
• Clarify two lines related to changes to the axe and sword skill trees.

Fixed

• Correct typos in the changelog.