associate arduino file-type with clang-format

[yayayaty]

Arduino (https://www.arduino.cc/) source files (.ino filename extension) are essentially a c++ files, but recognized as a separate file type by vim (for Arduino-specific syntax highlighting, I believe).
Arduino IDE, which uses .ino files for user source code, provides for external editor support, which could be vim.
I found it helpful to associate arduino files with clang-format, which works well for me.

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[yayayaty]

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