Summarise proportions of treatment response by two subgroups

Question

I generated the following random data which has the same structure as my real data:

data <- structure(list(gender = structure(c(1L, 2L, 1L, 2L, 2L, 1L, 1L, 
1L, 2L, 1L, 2L, 1L, 1L, 2L, 1L, 2L, 2L, 2L, 1L, 2L, 1L, 1L, 2L, 
2L, 2L, 2L, 1L, 1L, 2L, 1L, 1L, 2L, 2L, 2L, 1L, 2L, 1L, 1L, 1L, 
2L, 2L, 2L, 2L, 1L, 1L, 2L, 2L, 2L, 1L, 1L, 1L, 2L, 1L, 1L, 2L, 
2L, 2L, 1L, 1L, 2L, 1L, 2L, 1L, 2L, 2L, 1L, 1L, 2L, 1L, 1L, 2L, 
1L, 1L, 1L, 2L, 2L, 2L, 1L, 1L, 1L, 2L, 1L, 2L, 1L, 1L, 1L, 2L, 
2L, 2L, 1L, 1L, 1L, 1L, 2L, 2L, 1L, 2L, 2L, 2L, 1L), .Label = c("Female", 
"Male"), class = "factor"), treatment_response = structure(c(2L, 
2L, 1L, 2L, 1L, 1L, 2L, 2L, 2L, 1L, 2L, 1L, 2L, 2L, 1L, 1L, 2L, 
1L, 2L, 2L, 2L, 1L, 2L, 2L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 2L, 2L, 2L, 1L, 2L, 2L, 2L, 1L, 1L, 1L, 2L, 2L, 2L, 1L, 1L, 
2L, 1L, 1L, 1L, 1L, 2L, 1L, 1L, 1L, 1L, 2L, 1L, 2L, 2L, 2L, 2L, 
1L, 2L, 1L, 2L, 2L, 2L, 2L, 1L, 2L, 1L, 1L, 1L, 2L, 2L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 1L, 1L, 2L, 2L, 
1L, 2L, 1L), .Label = c("Non-responder", "Responder"), class = "factor"), 
    country = structure(c(1L, 3L, 9L, 7L, 2L, 2L, 6L, 6L, 4L, 
    9L, 5L, 7L, 3L, 2L, 8L, 8L, 10L, 3L, 1L, 1L, 9L, 2L, 5L, 
    5L, 2L, 7L, 5L, 1L, 6L, 10L, 7L, 10L, 2L, 10L, 1L, 4L, 6L, 
    8L, 9L, 4L, 3L, 6L, 1L, 8L, 7L, 3L, 2L, 10L, 7L, 6L, 1L, 
    9L, 8L, 4L, 8L, 7L, 3L, 5L, 3L, 4L, 7L, 4L, 8L, 4L, 5L, 6L, 
    8L, 1L, 7L, 5L, 8L, 1L, 7L, 10L, 8L, 1L, 9L, 8L, 6L, 6L, 
    10L, 7L, 3L, 6L, 5L, 10L, 2L, 1L, 9L, 5L, 5L, 10L, 2L, 6L, 
    10L, 4L, 8L, 7L, 9L, 8L), .Label = c("Switzerland", "Czech Republic", 
    "Denmark", "Iceland", "Netherlands", "Norway", "Portugal", 
    "Romania", "Sweden", "Finland"), class = "factor")), class = "data.frame", row.names = c(NA, 
-100L))

This is how it looks like

'data.frame':   100 obs. of  3 variables:
 $ gender            : Factor w/ 2 levels "Female","Male": 1 2 1 2 2 1 1 1 2 1 ...
 $ treatment_response: Factor w/ 2 levels "Non-responder",..: 2 2 1 2 1 1 2 2 2 1 ...
 $ country           : Factor w/ 10 levels "Switzerland",..: 1 3 9 7 2 2 6 6 4 9 ...

I wish to create a data.frame where the treatment_response is summarised by gender and country in percentages or proportions. For example, 60% (or 0.6) of males in Switzerland are responders and 40% are non-responder, similarly for females, etc.

I am familiar with the existence of dplyr and have managed to find a method to do this for mean but not for proportion or percentages.