JSON Block interface is not being exported in blockly.ts

[heliacer]

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Description

JSON Block interface got added in #9613 ,
but sadly can't be accessed.

It should be added to blockly.ts in the re-exports :D

Reproduction steps

No response

Priority

very easy to fix, just a single export

Stack trace

Screenshots

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Browsers

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[yuanran32]

I want to fix this issue. I will add the missing export in blockly.ts and create a PR later.