[mod] add /engine_descriptions.json endpoint

returns engine descriptions (JSON):
* key: engine name
* value: description in the user locale, use English description as a fallback

searx/webapp.py

@@ -54,6 +54,7 @@ from searx import (
     settings,
     searx_debug,
 )
+from searx.data import ENGINE_DESCRIPTIONS
 from searx.settings_defaults import OUTPUT_FORMATS
 from searx.settings_loader import get_default_settings_path
 from searx.exceptions import SearxParameterException
@@ -1140,6 +1141,23 @@ def image_proxy():
         return '', 400
 
 
+@app.route('/engine_descriptions.json', methods=['GET'])
+def engine_descriptions():
+    locale = get_locale().split('_')[0]
+    result = ENGINE_DESCRIPTIONS['en'].copy()
+    if locale != 'en':
+        for engine, description in ENGINE_DESCRIPTIONS.get(locale, {}).items():
+            result[engine] = description
+    for engine, description in result.items():
+        if len(description) ==2 and description[1] == 'ref':
+            ref_engine, ref_lang = description[0].split(':')
+            description = ENGINE_DESCRIPTIONS[ref_lang][ref_engine]
+        if isinstance(description, str):
+            description = [ description, 'wikipedia' ]
+        result[engine] = description
+    return jsonify(result)
+
+
 @app.route('/stats', methods=['GET'])
 def stats():
     """Render engine statistics page."""