message: Updates README for fmt
  Details changes from to axom's vendored copy of fmt
diff: @@ -11,3 +11,5 @@ We also put fmt in the axom namespace to isolate it from other libraries that mi
  > find . -type f -regex .*[.]h$ -exec sed -i "s/fmt::/axom::fmt::/g" {} \;
  * Add `namespace axom { \` to `AXOM_FMT_BEGIN_NAMESPACE` in `fmt/core.h`
  * Add `} \` to `AXOM_FMT_END_NAMESPACE` in `fmt/core.h`
  +* Apply `src/thirdparty/axom/fmt/xl_clang.patch` -- bugfix for XL compiler
  +* Apply `src/thirdparty/axom/fmt/hipcc_long_double.patch` -- bugfix for dealing with `long double` type on EAS architecture with hip compiler
  