[vim/en] Adding nohl information to the vim tutorial

[Rohan-Nair]

• [x] I solemnly swear that this is all original content of which I am the original author
• [x] Pull request title is prepended with [language/lang-code] (example [python/fr-fr] or [java/en])
• [x] Pull request touches only one file (or a set of logically related files with similar changes made)
• [x] Content changes are aimed at intermediate to experienced programmers (this is a poor format for explaining fundamental programming concepts)
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  • [x] Yes, I have double-checked quotes and field names!

Adding information about nohl in the tutorial to clear seach highlighting.