Add Arduino library property and metadata files

- Add library.properties with proper metadata and dependencies
- Add keywords.txt for Arduino IDE syntax highlighting
- Add MIT LICENSE file

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

LICENSE

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+MIT License
+
+Copyright (c) 2025 Adafruit Industries
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

library.properties

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+name=Adafruit BQ25628E Library
+version=1.0.0
+author=Adafruit
+maintainer=Adafruit <info@adafruit.com>
+sentence=Arduino library for BQ25628E I2C Battery Charger
+paragraph=This library provides functions to configure and monitor the Texas Instruments BQ25628E I2C battery charger chip. Features include charge current/voltage control, input limits, ADC measurements, status monitoring, and interrupt management.
+category=Device Control
+url=https://github.com/adafruit/Adafruit_BQ25628E
+architectures=*
+depends=Adafruit BusIO