readthedocs search optimization

[ottonemo]

readthedocs analytics says that we have several search results that yield little or no useful results. Let's improvethose:

• gpu (only 2 results): make sure that explanation of device parameter mentions gpu as well
• gridsearch (0 results): make sure to include the term gridsearch in the meta data of the GridSearchCV page (or similar)
• seed (0 results): think about a FAQ answer
• earlystop (0 results): make sure to include the earlystop keyword in the callbacks section

[BenjaminBossan]

Should we close this or leave it open as a reminder?

[ottonemo]

This was addressed in #879 and #836.