Fix #1255

Please do not use that special word @sahilbhosale63, because the entire issue would be closed when/if this is merged.

Let's just double check that there's no other instances that actually need changes in the command itself or its output.

UPDATE: I looked over the entire 33 instances of $ dvc add and this is what I found:

• /content/docs/command-reference/move.md:36 - the .dvc file that follows it in lines 42-8 needs to be updated (it should be much shorter now).
• content\docs\start\data-versioning.md:36 - git add command in line 46 could be reordered (put .gitignore at the end).
• content\docs\start\data-versioning.md:36 - same
• content\docs\use-cases\shared-development-server.md:82 - isgit add in line 85 missing .gitignore?
• content\docs\use-cases\versioning-data-and-model-files\index.md:46-7 - git add in line 63 could be reordered too.
• content\docs\use-cases\versioning-data-and-model-files\tutorial.md"125/147 - reorder git add in 156. Maybe also put data before model (same in line 235)
• content\docs\user-guide\dvc-files-and-directories.md:305 - probably remove ... line under it, and .dvc file example in lines 314-8 needs update
• content\docs\user-guide\how-to\update-tracked-files.md:51 - is git add in line 52 missing .gitignore?

^ For all these it's necessary to follow the entire example/context in question to determine these questions, and make the necessary updates.

Thanks @sahilbhosale63 !