Add docs section about upgrading

[nidico]

I just spend quite some stripping a false-positive issue down to a minimal reproducable testcase, until I noticed that I still had elm-review 2.11.1 installed and the bug has been fixed in 2.12.x.

I now understand - the review elm dependencies are managed just like any other elm project, and this also includes upgrades (e.g. through elm-json upgrade --unsafe). I just didn't think about it yet, as I already regularly checked whether the elm-review npm package is up-to-date (through npm outdated) - but well, this is another thing.

I'd propose to add a short section about how to keep "elm-review" (in its entirety) up-to-date, i.e. how to check for installed and available versions for both the elm-review CLI tool (the npm package) and the elm dependencies in review/elm.json, and how to perform upgrades for both.

[sparksp]

Where would you go to look for this information? Would it be the elm packages website or the npm package? Or would you come to one of the GitHub repos?

[nidico]

I was thinking about the package website README , which is the Github repo README of the main package.