There is no example in the "Math" block of "Blocks" document

[yanlxu]

Repro steps:
• Navigate to https://makecode.microbit.org/ (repro on all browser)
• Click the "Blocks" under the "?"
• Pull-down the document to the example "Math"
• Click the "Math" block

Expected result:
There is example in the "Math" block
Actual result:
There is no example in the "Math" block
Additional information:
The IE can't open the "Block" document in the first time, please refer to the second gif

[ganicke]

Added support for builtin docs in #2781.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.