Rename ignoring not found

For the mapping overloads of rename / rename! - I've at times wanted to ignore columns that aren't found.

  rename(df::AbstractDataFrame, (from => to)::Pair...)
  rename(df::AbstractDataFrame, d::AbstractDict)
  rename(df::AbstractDataFrame, d::AbstractVector{<:Pair})

I think an optional kwarg would be a reasonable extension of the api? (not sure on name)

julia> df = DataFrame(; a=[1, 2, 3], b=[4, 5, 6])
3×2 DataFrame
 Row │ a      b
     │ Int64  Int64
─────┼──────────────
   1 │     1      4
   2 │     2      5
   3 │     3      6


julia> rename(df, :a => :column_1, :c => :column_2)
ERROR: ArgumentError: Tried renaming :c to :column_2, when :c does not exist in the Index.

julia> rename(df, :a => :column_1, :c => :column_2; ignorenotfound=true)
3×2 DataFrame
 Row │ column_1  b
     │ Int64     Int64
─────┼─────────────────
   1 │        1      4
   2 │        2      5
   3 │        3      6

Start with the mapping overloads of rename and rename! described in the issue, including Pair, AbstractDict, and AbstractVector{<:Pair} inputs. Check how missing source columns currently raise errors and determine the final keyword argument name and behavior from the API discussion. Done means existing columns are renamed while missing columns are ignored when the option is enabled, with current behavior preserved by default.