rename edith (sao) to eydis

I first thought there were no pictures of this character on danbooru, now I found her with the tag edith_(sao)
To better find her, her common English Name translation from her Game Apperances and Official Media should be used. 

Sources:
Official Game Website: https://ab.sao-game.jp/en/gallery/eydis.html
Official Twitter: https://twitter.com/sao_risingsteel/status/1174287964492296192?lang=de

BUR #4796 has been approved by @evazion.

rename edith_(sao) -> eydis_(sao)

As per above.

The bulk update request #4796 (forum #181320) has been approved by @evazion.

BUR #6631 has been approved by @evazion.

create alias edith_(sao) -> eydis_(sao)

utility alias, the SAO Wikia has her name as 'Edith', no mention of 'Eydis' anywhere, also Pixiv has her name Romanized as 'Edith' (well, 'Edith Synthesis Ten')

The bulk update request #6631 (forum #193673) has been approved by @evazion.