Add yet-another-react-lightbox package and update .gitignore to exclude node_modules

frontend/node_modules/ajv/.tonic_example.js

@@ -1,20 +0,0 @@
-var Ajv = require('ajv');
-var ajv = new Ajv({allErrors: true});
-
-var schema = {
-  "properties": {
-    "foo": { "type": "string" },
-    "bar": { "type": "number", "maximum": 3 }
-  }
-};
-
-var validate = ajv.compile(schema);
-
-test({"foo": "abc", "bar": 2});
-test({"foo": 2, "bar": 4});
-
-function test(data) {
-  var valid = validate(data);
-  if (valid) console.log('Valid!');
-  else console.log('Invalid: ' + ajv.errorsText(validate.errors));
-}