images in README

[wibeasley]

excerpt of message sent by CRAN maintainer today:

...
Will Beasley wibeasley@hotmail.com: IalsaSynthesis

These have README.md referencing local images which do not get shipped with the package, and hence missing in the README.html we generated from the README.md for the CRAN package web pages. See the list of missing image files below.

Can you pls fix to either ship the missing image files with the package (in which case you could put them in a suitable subdirectory of 'tools'
in case things like 'vignettes' or 'man/figures' are not appropriate), or use URLs (e.g. from your package source code repositories) instead?
...

$IalsaSynthesis
[1] "libs/images/ialsa_wide.png"