feat(file-preview): allow preview of gherkin feature files (#412)

Author: ajclyall

AUTHORS.md

@@ -2,6 +2,7 @@
 
 The list of contributors in alphabetical order:
 
+- [Alastair Lyall](https://orcid.org/0009-0000-4955-8935)
 - [Alp Tuna](https://orcid.org/0009-0001-1915-3993)
 - [Audrius Mecionis](https://orcid.org/0000-0002-3759-1663)
 - [Daan Rosendal](https://orcid.org/0000-0002-3447-9000)

reana-ui/src/util.js

@@ -286,6 +286,7 @@ const customMime = new Mime(standardMimeTypes, otherMimeTypes, {
   // See https://github.com/root-project/root/issues/6771
   "application/x-root": ["root"],
   "text/x-python": ["py"],
+  "text/x-gherkin": ["feature"],
 });
 
 /**