add document for escaping file references in oras CLI

[qweeah]

Code of Conduct

• I have read and agree to the ORAS' Code of Conduct

What part of document/web-page on oras.land is affected?

oras CLI uses colon : as a delimiter of file path and media type in the file reference. If a file reference 1) doesn't contain mediatype and 2) file path contains colon, user should add colon at the end of reference.

# file path: my.file
# media type: file.media.type
oras push $REG/$REPO:$TAG my.file:file.media.type


# file path: my:file
# media type:N/A
oras push $REG/$REPO:$TAG my:file:

Additional comments?

This should be documented in oras.land so oras user can find it.

[TerryHowe]

Going to close oras-project/oras#734 ?