Update English translation

• 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

• Make sure every file ends with an empty line.
• Separate the percent sign (%) from its number by a space, to follow the ISO 31-0 standard.

Changed

• Replace the term "energy" with "stamina".
• Reduce the number of new lines inserted by the hud-skill-req_sp key.
• Rename weapon unlock skills.
• Simplify the description of the buff-stat-agility key.
• Miscellaneous changes to Fluent messages.

Fixed

• Add a period to skill descriptions and other messages for consistency.