Changed deprecated map function to modern tomap

[sitole]

map function was deprecated in Terraform v0.12 and recommended replacement is with tomap({ ... }).
Solves #12 issue

[squidfunk]

Perfect, thanks!

[maciejmajewski]

I think this still isn't working correctly on 0.15.

I am getting errors like:

│ On .terraform/modules/something.cors/headers.tf line 28: Expected an attribute value, introduced by an equals sign ("=").

key/value pairs should be delimited by =, syntax with , was specific for removed map function