runtime(arduino): Add Arduino ftplugin and indent files (vim/vim#14811)
We already have Arduino syntax file, but we didn't have ftplugin and
indent files.
This commit adds a basic ftplugin file and a basic indent file.
Both of them are derived from {ftplugin,indent}/c.vim.
957d903cb7
Co-authored-by: K.Takata <kentkt@csc.jp>
