[gatsby-plugin-mdx] timeToRead returns NaN if wordCount in Mdx component is 0

[JobenM]

Description

It's possible to have an mdx components without words for example we sometimes have embedded videos/ youtube.

So in this use case the getCounts function returns words property of undefined because the AST visitor never hits a word/paragraph. Thus the calculation for timeToRead (Math.round(words / avgWPM)) returns NaN.

I propose we fallback to 0 for these properties returned in getCounts and then timeToRead can default to 1.

Potential Fix

#30489

[vladar]

Thank you for the report and PR! 👍 I am closing this issue now that the PR is merged.