add gulp files and an explanation of build process options

gulpfile.js

@@ -0,0 +1,23 @@
+var gulp = require('gulp');
+const shell = require('gulp-shell');
+const changedInPlace = require('gulp-changed-in-place');
+const changed = require('gulp-changed');
+// var del = require('del');
+
+var paths = {
+  compile: ['*.scad'], // '**/*.scad',
+};
+
+gulp.task('compile', function() {
+  // recompile any changed openscad files
+  return gulp.src(paths.compile)
+             .pipe(changedInPlace({howToDetermineDifference: "modification-time"})) // TODO doesnt work for literally no reason
+             .pipe(shell([
+              //  'openscad compile/compile.scad -o compile/out.stl > 1'
+              'openscad <%= file.relative %> -o <%= file.relative %>.stl'
+            ], { verbose: true, shell: '/bin/bash'}))
+});
+
+gulp.task('default', function() {
+  gulp.watch(paths.compile, gulp.series('compile'));
+});