Don't hardcode Id for root

[aDotInTheVoid]

The Json ID's are opaque, and may be changed at any point (In fact, I;m: To quote the rfc:

They happen to be the compiler internal DefId for that item, but in the JSON blob they should be treated as opaque as they aren't guaranteed to be stable across compiler invocations.

In fact, Its possible rustdoc should mangle Ids, so they dont look human readable, because they arn't indended to convey any information themself.

Also: Thanks for writing this post, and I'm super glad to see people finding uses for rustdoc-json. Please file issues if you run into anything or can think of improvements to the json format.

[scrabsha]

Hi! Thank you for jumping in.

I was really worried by leaving hardcoded id in the blogpost but found no clean solution for this. Thanks!
I will definitely accept this PR, but i will need to do some small adjustments before that.

Thank you!

[scrabsha]

@aDotInTheVoid can I add a link to your github/twitter/anything else profile at the end of the post?

[aDotInTheVoid]

A link to my github would be lovely, thanks