This adds ignores for the yarn-debug.log* and yarn-error.log* files sometimes produced by the Yarn package manager.

Reasons for making this change:

Yarn, similar to npm, has log files that should be ignored.

Links to documentation supporting these rule changes:

Didn't find documentation, but here is code in Yarn that creates yarn-error.log:

• https://github.com/yarnpkg/yarn/blob/e2f4a3cf1b3cc863f078b68cf4f9195d0ebe423e/src/cli/index.js#L364

And here are some issues and PRs as evidence:

• Windows: Can't install global package; error log included yarnpkg/yarn#1600
• Yarn fails and doesn't provide information when running inside Docker yarnpkg/yarn#1460
• Add try/catch when writing yarn-error.log yarnpkg/yarn#2095

For yarn-debug.log, here's an issue comment as evidence:

• Cant run npm run dev. Give me a ENONT FILE error electron-react-boilerplate/electron-react-boilerplate#655 (comment)

As well as other projects I've found that ignore it:

• https://github.com/thebigredgeek/microlock/blob/a1c3279e63ddbb32713572c1461162309aec319c/.gitignore#L5
• https://github.com/calebmer/graphql-strong/blob/d0357619cc7eb43bb199616a780543eae145c799/.gitignore#L4