readme: fix reference to used dataset

readme: add more infos about re-trained model

readme: fix markdown

readme: mention potential bug in pretraining (truncated Wikipedia articles are used)

readme: fix revision of forked Helibrunna repo

readme: include some new logo :-)

readme: update information about final xLSTM model (one epoch over corpus)

readme: cleanup configuration example

readme: mention currently missing grad norm

readme: mention Tristan

readme: mention Tristan

readme: add more training details

readme: add example usage

readme: mention uploaded checkpoint

readme: update

readme: finalize training section

readme: minor tweaks

readme: add initial version

initial commit