Change WrapperArray.wrappers and WrapperArray.length to read-only

[38elements]

What problem does this feature solve?

WrapperArray.wrappers and WrapperArray.length are read-only in the type definition.
WrapperArray.wrappers and WrapperArray.length are not read-only.

What does the proposed API look like?

WrapperArray.wrappers and WrapperArray.length are read-only.

[38elements]

I will send a pull request widthin 7 days.