Helix additional settings

[andrexm]

• .config/helix/config.toml: add file picker settings, in order to hide git ignored files and show important hidden ones;
• .ignore: list files and directories to ignore and not to ignore in Helix.

If you like these suggestions, here are additional ones:

• add !.config to the Helix .ignore file (~/.ignore) and also other important files and directories that are present in this repository;