Escape backticks in stdout and stderr

[manabusakai]

Thank you for an awesome actions! 😄
fixes #401

The stdout of validate or plan may contain backticks. If backticks are included, problems like #401 will occur.

Fix this problem by escaping the backticks.

[hashicorp-cla]

All committers have signed the CLA.

[bflad]

Hi @manabusakai 👋 Thank you for submitting this.

This seems reasonable on the surface, however it is not clear whether this should be an automatic behavior of this particular GitHub Action. While you are passing the output to an action that is sensitive to particular characters, other workflows may be dependent on the existing behavior and introducing the escaping could introduce a regression. This submission does not do this, but just to mention, it also seems awkward to potentially introduce this as a configurable action option, for such a targeted use case.

While we wait for other maintainers to offer their opinions, you may want to check out other GitHub Actions that seem to implement this functionality, such as https://github.com/marketplace/actions/find-and-replace-strings. I cannot endorse this particular action as I have never used it myself, but it (or another similar action) should hopefully get the job done for your use case.

Thanks again.