Add support for the GAP language

lib/linguist/languages.yml

@@ -620,6 +620,16 @@ Forth:
   extensions:
   - .4th
 
+GAP:
+  type: programming
+  lexer: Text only
+  primary_extension: .g
+  extensions:
+  - .g
+  - .gap
+  - .gd
+  - .gi
+
 GAS:
   type: programming
   group: Assembly

lib/linguist/samples.json

@@ -129,6 +129,11 @@
       ".forth",
       ".fth"
     ],
+    "GAP": [
+      ".g",
+      ".gd",
+      ".gi"
+    ],
     "GAS": [
       ".s"
     ],