I often use Sublime Text 3 for creating LaTeX documents. When doing so I really need spell checking for my texts to avoid producing gibberish. Fortunately that feature is already included, only dictionaries have to be added to support you preferred language.
Here you can find basic information on how to achieve that from the official homepage.
Unfortunately it wasn’t self explanatory to me. To get new dictionaries working, go to https://github.com/titoBouzout/Dictionaries, select the language you are looking for and make sure to download the raw version. If you just save the link via right click you will save the GitHub page and not the raw file. Place the .dic and .aff files in Packages/User/ and follow the instructions from the official site.
Credit goes to mara, who answered this question on stackoverflow