Revise Troubleshooting.md

[ddbeck]

After having a bit of difficulty with the troubleshooting steps in a previous issue, I've tried to revise the Troubleshooting document to:

• make the doc easier to follow top to bottom (e.g., putting troubleshooting steps in order of specificity, putting issue contents guidelines after all of the troubleshooting steps, and adding some section signposting)
• rephrase things to capture formula-related problems that are not explicitly build failures

I also tweaked a few things here and there to be (hopefully) more readable. Thanks for considering my PR!

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• [N/A] Have you written new tests for your changes? Here's an example.
• Have you successfully run brew tests with your changes locally?

[MikeMcQuaid]

One small comment otherwise this looks great and is an improvement, thanks!

[MikeMcQuaid]

Would rather leave this at the top as people often don't read more than the first line here, sadly.

[scpeters]

I agree, thanks for clarifying the debugging steps!

[ddbeck]

OK, I've brought back the attention-grabbing first line and tweaked the introduction to match up with that a little better. Let me know if you want to see any other changes. Thanks!

[MikeMcQuaid]

Thanks for your contribution to Homebrew! Without people like you submitting PRs we couldn't run this project. You rock!