[WIP] #89 Re-enable Psalm

[hkirsman]

Overview

Re-adding Psalm, but it's 7.x dev. As far as I understand, that's the only way possible atm.

Screenshots

Testing

1. Install this update
   composer require wunderio/code-quality:dev-feature/89-Upgrade-Psalm --dev --with-all-dependencies

2. Run Psalm:
   ddev grumphp run --tasks=psalm

[vermario]

dev-master has a conflicting requirement with grumphp:

Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Root composer.json requires wunderio/code-quality dev-feature/89-Upgrade-Psalm -> satisfiable by wunderio/code-quality[dev-feature/89-Upgrade-Psalm].
    - phpro/grumphp[v2.5.0, ..., v2.x-dev] require amphp/amp ^3.0 -> satisfiable by amphp/amp[v3.0.0-beta.1, ..., 3.x-dev].
    - vimeo/psalm 6.x-dev requires amphp/amp ^2.4.2 -> satisfiable by amphp/amp[v2.4.2, ..., 2.x-dev].
    - vimeo/psalm dev-master requires nikic/php-parser ^5.0.0 -> found nikic/php-parser[dev-master, v5.0.0alpha1, ..., v5.4.0] but these were not loaded, likely because it conflicts with another require.
    - wunderio/code-quality dev-feature/89-Upgrade-Psalm requires phpro/grumphp ^2.5 -> satisfiable by phpro/grumphp[v2.5.0, ..., v2.x-dev].
    - wunderio/code-quality dev-feature/89-Upgrade-Psalm requires vimeo/psalm 6.x-dev -> satisfiable by vimeo/psalm[6.x-dev (alias of dev-master)].
    - Conclusion: don't install amphp/amp v2.6.4 (conflict analysis result)
    - Conclusion: don't install amphp/amp v3.0.2 (conflict analysis result)
    - You can only install one version of a package, so only one of these can be installed: amphp/amp[v2.2.0, ..., 2.x-dev, v3.0.0-beta.1, ..., 3.x-dev].
    - vimeo/psalm 6.x-dev is an alias of vimeo/psalm dev-master and thus requires it to be installed too.

I noticed that instead the 6.x dev version still points to the old version: https://packagist.org/packages/vimeo/psalm#6.x-dev I wonder if we could try that?