[Search] Search frontend plugin (#3086)

* feat(search) search plugin

* feat(search): search page components

* feat(search): api

* feat(search): filters wip

* feat(search): wip filters

* fix(search): delete unused useParams hook

* fix(search): update docs

* fix(search): use latest versions of dependencies

* fix(search): change version of catalog plugin

* fix(search api): pass instance of catalog api to search api

* fix(filters): rename component from FilterButton to FiltersButton

* fixup

* fix(filters): use list of checkboxes to match style of catalog page filters

* fix(styles): use theme spacing for margins and paddings, delete unused styles

* fix(search): change terminology of search input to be more consistent and clear

* fix(search): restructure component exports according to ADR

* fix(search): replace sm with xs on Grid components to support smaller screens

* fix(search): add types

* fixup

* fix(search): bump backstage core

* change versions of backstage theme and dev-utils

plugins/search/dev/index.tsx

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2020 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { createDevApp } from '@backstage/dev-utils';
+import { plugin } from '../src/plugin';
+
+createDevApp().registerPlugin(plugin).render();