Add example of doc generation with metaprogramming (JuliaLang#15363)

doc/src/manual/documentation.md

@@ -317,6 +317,23 @@ end
 will add documentation to `f(x)` when `condition()` is `true`. Note that even if `f(x)` goes
 out of scope at the end of the block, its documentation will remain.
 
+It is possible to make use of metaprogramming to assist in the creation of documentation.
+When using string-interpolation within the docstring you will need to use an extra `$` as
+shown with `$($name)`:
+
+```julia
+for func in (:day, :dayofmonth)
+ name = string(func)
+ @eval begin
+ @doc """
+ $($name)(dt::TimeType) -> Int64
+
+ The day of month of a `Date` or `DateTime` as an `Int64`.
+ """ $func(dt::Dates.TimeType)
+ end
+end
+```
+
 ### Dynamic documentation
 
 Sometimes the appropriate documentation for an instance of a type depends on the field values of that