add a section to better document string representations

[bashbaug]

Currently, there is minimal information in the OpenCL specification about strings that are passed into and out of OpenCL, and it is in a footnote:

https://registry.khronos.org/OpenCL/specs/3.0-unified/html/OpenCL_API.html#_footnotedef_3

A null terminated string is returned by OpenCL query function calls if the return type of the information being queried is a char[].

We should better document the behavior for strings passed into and out of OpenCL, such as the expected string encoding, whether strings are null-terminated, etc. As one possibility, we could add "string representations" section similar to the one in Vulkan specification:

https://registry.khronos.org/vulkan/specs/latest/html/vkspec.html#fundamentals-strings