Ensure position = "inside" works

[teunbrand]

I am sorry about the possibility of interrupting your vacation.

Could you please tell me if there is a possibility that the parameters such as position = 'inside' or theme = theme(legend.position = 'inside) in guide_colbar could be adjusted in the future to be similar to those similar to guide_colorbar in ggplot2.
Right now it doesn't seem to be able to put the colorbar into the panel, and I'm not quite sure if it's the same due to this bug.

Originally posted by @Breeze-Hu in #41 (comment)