webpack build gets stuck when using certain markdown syntax #265

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Bug report

Version

v0.6.7

Steps to reproduce

Download this and follow the repro steps in README.md

It gets stuck when using $$\frac{A_1B_2}{C}$$ in markdown with @iktakahiro/markdown-it-katex

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What is expected?

webpack build succeeds.

What is actually happening?

webpack build gets stuck.

Other relevant information

• Result of running saber -v:
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• Is Saber a global or local install?
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• Does this issue occur when all plugins are disabled?