Update README.md

Author: Kevin-OConnor

README.md

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 # 2026Beta
 Repository for Beta Testing of 2026 Software
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+>**Software posted here is Beta software for the 2026 season and is not compatible with 2025 software or roboRIO images.**
+
+Note that all updated documentation for 2026 changes, new features, etc. can be found on the 'latest' version of the WPILib Docs site: https://docs.wpilib.org/en/latest/.
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+## Beta Software Directory
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+### Vendor Libraries
+
+### Other