Fix showndown format import

[Aelysya]

Description

This MR fixes the showndown import process not working in some specific cases.

The array containing Pokémon that have an hyphen '-' in their name has been completed to avoid false positives on alternative forms.

The conversion to DbSymbol from a string has been completed to include usual special characters like ', : or .
The conversion also includes a normalization to remove accents from letters.

Note before testing

Here's a template to test different cases on:

POKEMON_NAME
Ability: Overgrow
- King's Shield
- Land's Wrath

Tests to perform

• Test the import process with Pokémon without special characters in their name, the importation still works correctly
• Test the import process with Pokémon with special characters in their name, the importation works correctly (examples: Jangmo-o, Ho-oh, Type: Null, Farfetch'd, Mr. Mime)
• Test the import process with moves with special characters in their name, the importation works correctly (examples are included in the template above)