If this doesn't work, for me I Downloaded the file, then in Notepad++ in the language menu - > User Defined Language -> Define your language... Then click Import and select the gherkin.xml file and save as. Then enter the name you want for it e.g. Gherkin1 then when you open a new file if you click Language, at the bottom under User Defined should be your saved language and if you click it it applies.
If this doesn't work, for me I Downloaded the file, then in Notepad++ in the language menu - > User Defined Language -> Define your language... Then click Import and select the gherkin.xml file and save as. Then enter the name you want for it e.g. Gherkin1 then when you open a new file if you click Language, at the bottom under User Defined should be your saved language and if you click it it applies.