Include tags posts and make them searchable [Feature Request]

[bblodfon]

It would be great if for every post we assign some tags (on submission or even after) and someone is able to search through them in a simple box on the starting page (https://mlr-org.com/gallery.html), e.g. if I write one of the following: "survival", "tuning", "impute", "pipelines", "missing", "density", "xgboost", etc. then I would get all posts with the aforementioned tag of interest.