Using the Atom package manager:
apm install lint-yalafi
You also have to install linter:
apm install linter
Since this is an interface to YaLafi it also has to be installed. The easiest way is to use
pip install yalafi
If you do not want to use the LanguageTool online server you also need to install Java and LanguageTool. More information on how to install LanguageTool can be found here.
Then you can set the 'LanguageTool path' in the settings.
It should point to the directory containing e.g. 'languagetool-server.jar'.
This package will then start the server if it is not already running.
You can also start the server manually by invoking YaLafi yourself, e.g. with
python -m yalafi.shell --lt-server my file.tex.
For even better spell-checking one can use n-gram data to find errors with words that are often confused. More information and the n-gram data can be found here. After downloading and unzipping, you have to set the 'LanguageTool path for n-gram data' in the settings.
Important: The 'LanguageTool server options' and also the n-gram data path is only used at first server startup. Just changing the settings will not give you any results unless you manually kill the server.
Good catch. Let us know what about this package looks wrong to you, and we'll investigate right away.