Update website doc of init orca context (#2879)
Update website doc of init orca context (#2879)

* update doc

* update
intel-analytics/BigDL,yangw1234/BigDL,intel-analytics/BigDL,intel-analytics/BigDL,yangw1234/BigDL,yangw1234/BigDL,yangw1234/BigDL,intel-analytics/BigDL