Add datasets from Bonham Thesis

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this thesis page 26 has more datasets.

• Spanish Sign Language: María del Carmen Cabeza-Pereiro (cabeza@uvigo.es)
• Estonian Sign Language: ?
• Finnish Sign Language: Juhana Salonen, Antti Kronqvist (juhana.salonen@jyu.fi, antti.r.kronqvist@jyu.fi)
• Danish Sign Language: Jette H. Kristoffersen, Thomas Troelsgård (jehk@ucc.dk, ttro@ucc.dk)
• GSL - https://arxiv.org/pdf/2007.12530.pdf
• Phoenix SD / SI - J. Forster, C. Schmidt, O. Koller, M. Bellgardt, and H. Ney, "Extensions of the sign language recognition and translation corpus rwth-phoenixweather." in LREC, 2014, pp. 1911–1916.
• Noema+ GSL dictionary (Efthimiou et al., 2016),
• BSL signbank (Jordan et al., 2014),
• NGT global signbank (Crasborn et al., 2020)