Array.findLast and other missing functions

[jmagaram]

Some missing functions from the Array module. In particular the findLast variants.

indexOfFromOpt: add code and docs
lastIndexOf : docs, tests
lastIndexOfOpt : tests
lastIndexOfFrom : docs, tests
findLast : code, docs, tests
findLastIndex : code, docs, tests
findLastIndexOpt : code, docs, tests
findLastIndexWithIndex : code, docs, tests
findLastIndexWithIndexOpt : code, docs

[jmagaram]

I have no idea why the tests aren't working. It works for me.

[glennsl]

It fails because the function does not exist in Node.js 16. Node.js 16 is included in the CI matrix because it's a Long Term Support release. It will stop being supported in September, at which point the matrix should be updated and the checks should pass.

[cvoight]

Now that Node.js 16 has reached end-of-life, will this be merged for the next release? And thanks, Justin; I needed findLastIndex!