Conditionally show live examples based on feature detection about interactive-examples

[schalkneethling]

If any of the syntax variants are not supported in the current browser, show the static code example within the iframe. This will then be accompanied by a message to the user to indicate that their browser does not support the current feature or parts thereof.

Perhaps with an in-document link to the support tables? @stephaniehobson @wbamberg

[schalkneethling]

@stephaniehobson On this one, should we include a custom build of https://modernizr.com/download?setclasses or should we roll our own that we build up over time as we need extra checks?

[schalkneethling]

Here is the final decision on how we are going to implement this:
https://github.com/mdn/interactive-examples/wiki/Weekly-Meeting-Notes#conclusion

[schalkneethling]

@stephaniehobson @wbamberg Before this one out, what is our definition of supported? Is it as per spec non vendor prefixed?

[stephaniehobson]

I think the stated preference is to write examples without vendor prefixes which means they won't run without the vendor prefix. But maybe we do want to have some kind of allowance for vendor prefixes in interactive examples? But that means showing the -webkit- prefix to the Firefox users and that normally won't work in FF and we'll have to update the example as support evolves....

I think the short answer here is I don't know either.

[wbamberg]

I think for a first version we should not use prefixes. Do you have a feeling for how big an issue this is? Would it cause us to exclude a lot of properties that we could otherwise include?