Added topics for luhn

Update config.json

topics properly spaced for series

Added topics for minesweeper

added topics for word search

;)

Update allergies topics as in #827

added topics for difference-of-squares

added topics for word search

added topics for the queen-attack problem

Update nucleotide-count topics as in #808

Add topics for largest-series-product

Added @FridaTveit suggestions to nucleotide-count topics

* Updated Food-Chain Topics :)

* Removing plus signs from tags for food-chain

* minus comma

Added four tags to nucleotide-count topics as described in #808.

Add topics for acronym

Add topics to beer-song exercise

Add topics for space-age

Adding the list of topics for the phone-number problem

Add topics to pangram exercise

Add topics to twelve-days exercise

Adding the prerequisites to the CONTRIBUTING.md file

Add topics to raindrops exercise

* issue fixed

* minor bug fixed

* issue fixed #789

* minor bug fixed

Add Isogram topics