Add minimal support for recognizing OpenSCAD files.

As 3D printing becomes more popular, more OpenSCAD projects will appear
on github. This change allows linguist to recognize those projects.
Hopefully, this will make finding projects easier.

lib/linguist/languages.yml

@@ -1509,6 +1509,12 @@ OpenEdge ABL:
   extensions:
   - .p
 
+OpenSCAD:
+  type: programming
+  lexer: Text only
+  extensions:
+  - .scad
+
 Org:
   type: prose
   lexer: Text only

samples/OpenSCAD/not_simple.scad

@@ -0,0 +1,13 @@
+// A more complicated 3D shape in OpenSCAD
+$fn=32;
+
+difference() {
+    // main shape
+    union() {
+        translate( [ 0, 0,  2 ] ) cube( [ 15, 15, 4 ], center=true );
+        translate( [ 0, 0, 13 ] ) cylinder( h=25, r1=5, r2=3, center=true );
+        translate( [ 0, 0, 28 ] ) sphere( r=6 );
+    }
+    // hole through center
+    translate( [ 0, 0, 17 ] ) cylinder( h=35, r=2, center=true );
+}

samples/OpenSCAD/simple.scad

@@ -0,0 +1,3 @@
+// Simple sphere in OpenSCAD
+
+sphere( r=10 );