Support multiple input-filters to configure content to index via khoj.yml

- Update existings code, tests to process input-filters as list
  instead of str
- Test `text_to_jsonl' get files methods to work with combination of
  `input-files' and `input-filters'

Resolves #84

src/search_type/image_search.py

@@ -241,7 +241,11 @@ def setup(config: ImageContentConfig, search_config: ImageSearchConfig, regenera
         image_directories = [resolve_absolute_path(directory, strict=True) for directory in config.input_directories]
         absolute_image_files = set(extract_entries(image_directories))
     if config.input_filter:
-        filtered_image_files = set(glob.glob(get_absolute_path(config.input_filter)))
+        filtered_image_files = {
+            filtered_file
+            for input_filter in config.input_filter
+            for filtered_file in glob.glob(get_absolute_path(input_filter))
+        }
 
     all_image_files = sorted(list(absolute_image_files | filtered_image_files))