Configure SwiftLint's inclusive_language rule

This configures [SwiftLint's inclusive language rule][0].

We use "master key" and "profile whitelist" across Signal, so we allow
those terms. Everything else should be marked as a violation.

[0]: https://realm.github.io/SwiftLint/inclusive_language.html

.swiftlint.yml

@@ -12,6 +12,8 @@ opt_in_rules:
 - attributes
 attributes:
   always_on_line_above: ["@objc"]
+inclusive_language:
+  override_allowed_terms: ["master", "whitelist"]
 large_tuple:
   warning: 4
   error: 4