Validation of Czech versions of questionnaires assessing functional impairment in patients with systemic sclerosis: Scleroderma Health Assessment Questionnaire (SHAQ), Cochin Hand Functional Scale (CHFS), Mouth Handicap in Systemic Sclerosis (MHISS), UCLA Scleroderma Clinical Trial Consortium Gastrointestinal Tract 2.0 (UCLA SCTC GIT 2.0)