wcm: also take into account the icon path of wf-plugin

[dkondor]

Follow up on #124 -- otherwise, icons would not be found.

[soreau]

This PR seems fine but I'm a little confused because so far, icons have been housed in wcm, not with the plugins. Can you explain how the icon setup works for wayfire-plugin or link to documentation about it?

[dkondor]

Hi,
WCM provides icons for the "official" set of plugins, but not for third-party ones of course. I'm not sure if there is a recommended / documented way, but e.g. in my wstroke plugin, so far things worked by installing an icon to where Wayfire would put it, see here. This does not work anymore if installed with wayfire-plugin as the icon ends up under ~/.local/share/wayfire/plugin-manager/install/... (see here for the adjustments I'm currently planning to make this work at all; note that I already have some hacks to make the config GUI work, but that's a separate issue).

[soreau]

Thanks for explaining. I kinda wish that the paths that wayfire-plugin used matched the paths used in the wayfire install prefix, but I think that ship has sailed already. Thanks for the PR, merging..