Autocomplete for mentions should ignore diacritics

#### Is your feature request related to a problem?

Sometimes I want to mention users that have diacritics in their name, for example "Hỏaqgīo". Because typing diacritics is difficult on my phone, I try just typing "@ h o" to autocomplete the name, but then realize that Element's autocomplete is diacritic-sensitive, which is unexpected coming from Element Web. I then have to go back and type in the specific diacritics manually.

#### Describe the solution you'd like.

Element Android should ignore diacritics when autocompleting users, so that typing "@ h o" autocompletes a user named Hỏaqgīo.