Recreating the intention of PR #1816 explaining "make not found error"

[ysuarez]

Purpose / why

This PR essentially recreates older PR #1816 ("Added "make command not found" failure fix") since that PR's contributor never provided a signed CLA. A few attempts were made to contact the contributor to request a CLA from contributor to no avail, and DIG decided to just recreate the PR. Turns out that this older PR changed file docs/installation/docker-compose.md which was then deleted by PR #1797.

What changes were made?

The content explaining how to solve the make command not found error was moved to the top of docs/installation/docker-troubleshooting.md

I wondered if it should appear also in other spots when users are first asked to run make demo or make local, though it might be best to just be placed in a central location like docs/installation/docker-troubleshooting.md

Verification

Try running make demo or make local without make installed and see if the make installation steps work.

Interested Parties

@Islandora/documentation @Islandora/8-x-committers

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Checklist

Pull-request reviewer should ensure the following

• Does this PR link to related issues?
• Does the proposed documentation align with the Islandora Documentation Style Guide?
• Are the changes accurate, useful, free of typos, etc?
• Does this PR update the last updated on date on the documentation page?

Person merging should ensure the following

• Does mkdocs still build successfully? (This is indicated by TravisCI passing. To test locally, and see warnings, see How To Build Documentation.)
• If pages are renamed or removed, have all internal links to those pages been fixed?
• If pages are added, have they been linked to or placed in the menu?
• Did the PR receive at least one approval from a committer, and all issues raised have been addressed?