Protection against clang-format

Running clang-format on a piece of code such as `EM_ASM(a !== b);` results in `a != = b` (note broken code with space)

It appears clang-format doesn't understand that the code inside EM_ASM is javascript and shouldn't be reformatted.
One can somewhat workaround this with `// clang-format [on|off]` comments, but they need to be repeated at each callsite.
This bug is about recommending a best practice when using both clang-format & emscripten.

Possible approaches

Perhaps the EM_ASM macro could be marked up to indicate embedded JS & for clang-format to ignore it or use different formatting rules. Clang-format has support for this via RawStringFormats option which allows embedded code to be tagged e.g. `R"this-is-js(alert("Hello");)this-is-js"` but I didn't find a way to combine raw strings with the preprocessing stringizing.

Another option is to provide users with macros for passing raw strings instead of implicitly stringizing. e.g. one might write `EM_ASM_R( R"js( a!==b; )js" )`