Add module export detection (#505)

Allow modules to include a module_exports.lua file in their root which
will cause the file save/modules/module_name.lua to be generated
pointing to the exports file.

test/host/patch.js

@@ -28,6 +28,30 @@ describe("host/patch", function() {
 				}
 			});
 		});
+
+		describe("loadFiles()", function() {
+			const testModule = new patch.SaveModule(new lib.ModuleInfo("test", "1.0.0"));
+			const referenceFiles = new Map([
+				["modules/test/test.lua", "-- test\n"],
+				["modules/test/module_exports.lua", "-- module_exports\n"],
+				["locale/en/test.cfg", "module-test=A Test\n"],
+				["locale/en/test-locale.cfg", "module-test-locale=Test Locale\n"],
+				["modules/test.lua", "return require(\"modules/test/module_exports\")"],
+			]);
+			before(async function() {
+				await testModule.loadFiles("test/file/modules/test");
+			});
+			it("Should read the contents of all files in a module", function() {
+				assert.equal(testModule.files.size, referenceFiles.size);
+				for (let [relativePath, contents] of referenceFiles) {
+					if (!testModule.files.has(relativePath)) {
+						assert.fail(`Module is missing file: ${relativePath}`);
+					} else {
+						assert.equal(testModule.files.get(relativePath).toString("utf-8"), contents);
+					}
+				}
+			});
+		});
 	});
 
 	describe("generateLoader()", function() {