biojs-vis-sequence: Add 'pos-marker' class to index.
biojs-vis-sequence: Add 'pos-marker' class to index.

To allow styling from outside the widget.

Signed-off-by: Anurag Priyam <6e6ab5ea9cb59fe7c35d2a1fc74443577eb60635@gmail.com>

yeban/sequenceserver,aldermossy/sequenceserver,vivekiitkgp/sequenceserver,vivekiitkgp/sequenceserver,IsmailM/sequenceserver,lepbase/lepbase-sequenceserver,aldermossy/sequenceserver,elsiklab/sequenceserver,yeban/sequenceserver,deepakunni3/sequenceserver,yeban/sequenceserver,lepbase/lepbase-sequenceserver,deepakunni3/sequenceserver,aldermossy/sequenceserver,vivekiitkgp/sequenceserver,aldermossy/sequenceserver,elsiklab/sequenceserver,IsmailM/sequenceserver,yeban/sequenceserver,elsiklab/sequenceserver,lepbase/lepbase-sequenceserver,jasminZ/sequenceserver,jasminZ/sequenceserver,jasminZ/sequenceserver,deepakunni3/sequenceserver,IsmailM/sequenceserver