feat: Add `ParseXFile` for cross-platform `XFile` support

[mbfakourii]

Pull Request

• Report security issues confidentially.
• Any contribution is under this license.
• Link this pull request to an issue.

Issue

Add ParseXFile for support XFile.

Closes: #989

Approach

Tasks

• [ ] Add tests
• [ ] Add changes to documentation (guides, repository pages, code comments)

[parse-github-assistant[bot]]

Thanks for opening this pull request!

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 64 lines in your changes are missing coverage. Please review.

Project coverage is 43.37%. Comparing base (540b127) to head (09289a6).

Files	Patch %	Lines
packages/dart/lib/src/objects/parse_x_file.dart	0.00%	62 Missing :warning:
packages/dart/lib/src/objects/parse_file.dart	0.00%	1 Missing :warning:
packages/dart/lib/src/objects/parse_file_web.dart	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #990 +/- ## ========================================== - Coverage 44.16% 43.37% -0.80% ========================================== Files 60 61 +1 Lines 3401 3463 +62 ========================================== Hits 1502 1502 - Misses 1899 1961 +62 ```

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[mtrezza]

Is this ready for merge?

[mbfakourii]

Is this ready for merge?

Yes, I think it is ready to merge.

[mtrezza]

I just noticed that the docs workflow was skipped; shouldn't docs be published?

https://github.com/parse-community/Parse-SDK-Flutter/actions/runs/8493279325/job/23267194136

[mbfakourii]

I just noticed that the docs workflow was skipped; shouldn't docs be published?

https://github.com/parse-community/Parse-SDK-Flutter/actions/runs/8493279325/job/23267194136

I think this section had a problem in ci.

[mtrezza]

I tried to run it manually but it also wouldn't run. I'll look into it. https://github.com/parse-community/Parse-SDK-Flutter/issues/991