chore(gatsby-plugin-mdx): refactored to use createContentDigest (#8805)

[Stan-RED]

Description

gatsby-plugin-mdx refactored to use createContentDigest helper

Related Issues

#8805 feat: update gatsby plugins to use new createContentDigest helper

[muescha]

please see this comment: #18139 (review)

[muescha]

hi @StanEgo it is similar to #20076
if you don't have time i would like complete it

[Stan-RED]

Hi @muescha. Check please if this is what you've asked for.

[muescha]

yes - thx :)

but the @gatsbyjs/core core team has to approve & merge the PR

[pvdz]

Thanks :)

[gatsbot]

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