fix: if image starts with 'ipfs://', the return value should be string type

[GinMu]

Explanation

return promise value if image starts with 'ipfs://' at ERC721Standard.ts

References

Changelog

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've highlighted breaking changes using the "BREAKING" category above as appropriate
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes

[mcmire]

Hi @GinMu, thanks for submitting this PR. Glancing at the code there does seem to be a bug with getDetails in the case you highlighted.

It would be good to have a test which confirms the bugfix and then we can merge this. If you'd like to add this then that would be great, but otherwise we could do that. That's the only blocker I can see for this PR.

[GinMu]

Hi @mcmire , have added test case.