Big structure changes (check commit description)

- Moved most of the parser functions/files to the core package.
- Converted tools file to a package and made separate files for similar functions.
- Now all fetcher engines return a Response object
- Instead of selecting an engine to use and passing config to it, we have separate fetcher classes so the user can choose what to use while importing.
- I added a new custom fetcher so the user can create and use an engine.
- More...

scrapling/engines/toolbelt/__init__.py

@@ -0,0 +1,18 @@
+from .fingerprints import (
+    get_os_name,
+    generate_headers,
+    generate_convincing_referer,
+    generate_suitable_fingerprint,
+)
+from .custom import (
+    Response,
+    do_nothing,
+    BaseFetcher,
+    get_variable_name,
+    check_type_validity,
+    check_if_engine_usable,
+)
+from .navigation import (
+    js_bypass_path,
+    construct_websocket_url,
+)