Update file.js

[adamreisnz]

See #129.
Make it clearer that the examples below contain information on how to set file meta data.

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[adamreisnz]

I signed it!

[googlebot]

CLAs look good, thanks!

[stephenplusplus]

Awesome, thanks for this. Sometimes, I completely miss the obvious stuff. Feel free to send more PRs if you catch more of these!

[adamreisnz]

@stephenplusplus No worries, will do!