Fix: Renovate should create upgrades for WordPress versions where the patch version is 0 (e.g. 5.9.0)

Closes #111 (closed)

This MR switches from the default semver versioning to semver-coerced, which is more forgiving:

This versioning provides a very forgiving translation of inputs in non-strict-SemVer format into strict SemVer. For example, "v1" is coerced into "1.0.0", "2.1" => "2.1.0", "~3.1" => "3.1.0", "1.1-foo" => "1.1.0". Look at the Coercion section of this page for more info on input coercion.

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