Allow instantiated reporters to be provided in the configuration

This supports more complex scenarios than the --reporter= CLI flag
(multiple reporters, reporters that need configuration, reporters
that aren't default exports, etc) without pushing the complexity of
all of those scenarios into Jasmine or requiring the user to move
to programmatic usage.

See #77 and #159.

lib/jasmine.js

@@ -384,6 +384,24 @@ class Jasmine {
     if(config.spec_files) {
       this.addMatchingSpecFiles(config.spec_files);
     }
+
+    /**
+     * An array of reporters. Each object in the array will be passed to
+     * {@link Jasmine#addReporter|addReporter}.
+     *
+     * This provides a middle ground between the --reporter= CLI option and full
+     * programmatic usage. Note that because reporters are objects with methods,
+     * this option can only be used in JavaScript config files
+     * (e.g `spec/support/jasmine.js`), not JSON.
+     * @name Configuration#reporters
+     * @type Reporter[] | undefined
+     * @see custom_reporter
+     */
+    if (config.reporters) {
+      for (const r of config.reporters) {
+        this.addReporter(r);
+      }
+    }
   }
 
   addRequires(requires) {

spec/jasmine_spec.js

@@ -385,6 +385,17 @@ describe('Jasmine', function() {
 
         expect(this.fixtureJasmine.alwaysListPendingSpecs_).toBeTrue();
       });
+
+      it('adds specified reporters', function() {
+        const reporter1 = {id: 'reporter1'};
+        const reporter2 = {id: 'reporter2'};
+        this.configObject.reporters = [reporter1, reporter2];
+
+        this.fixtureJasmine.loadConfig(this.configObject);
+
+        expect(this.fixtureJasmine.env.addReporter).toHaveBeenCalledWith(reporter1);
+        expect(this.fixtureJasmine.env.addReporter).toHaveBeenCalledWith(reporter2);
+      });
     });
 
     describe('from a file', function() {