Multiple assignment errors Int to double

[MontiniCristian]

Same of #6

Flare-Flutter/lib/flare/actor_shape.dart:138:26: Error: A value of type 'dart.core::int' can't be assigned to a variable of type 'dart.core::double'.
compiler message: Try changing the type of the left hand side, or casting the right hand side to 'dart.core::double'.
compiler message: double maxStroke = 0;

Flare-Flutter/lib/flare/actor_skin.dart:31:28: Error: A value of type 'dart.core::int' can't be assigned to a variable of type 'dart.core::double'.
compiler message: Try changing the type of the left hand side, or casting the right hand side to 'dart.core::double'.
compiler message: _boneMatrices[0] = 1;