Return ImageSharp to System.Drawing alternatives list.

[JimBobSquarePants]

Summary

Following the publishing of the style guide docs and addition of ImageSharp to those docs in dotnet/docs#33533 this PR re-adds ImageSharp to the recommended list of alternatives to System.Drawing on non-Windows OS.

cc\ @richlander

[ghost]

Tagging subscribers to this area: @dotnet/area-system-drawing
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Summary

Following the publishing of the style guide docs and addition of ImageSharp to those docs in dotnet/docs#33533 this PR re-adds ImageSharp to the recommended list of alternatives to System.Drawing on non-Windows OS.

cc\ @richlander

Author:	JimBobSquarePants
Assignees:	-
Labels:	area-System.Drawing, community-contribution
Milestone:	-

[learn-build-service-prod]

Learn Build status updates of commit 08c00e4:

✅ Validation status: passed

File	Status	Preview URL	Details
includes/drawing.md	✅Succeeded	View

For more details, please refer to the build report.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

[learn-build-service-prod]

Learn Build status updates of commit e6ee63d:

✅ Validation status: passed

File	Status	Preview URL	Details
includes/drawing.md	✅Succeeded	View

For more details, please refer to the build report.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

[BillWagner]

Thanks @JimBobSquarePants

This LGTM, and I'll now.

/cc @richlander