Add note about UrlEncode

[ManickaP]

UrlEncode is suitable only for query segment or x-www-form-urlencoded content. Also the list of unescaped punction doesn't follow neither URI RFC (old or new) nor any other spec I could find.

[learn-build-service-prod[bot]]

Learn Build status updates of commit 11eb380:

:warning: Validation status: warnings

File	Status	Preview URL	Details
xml/System.Net/WebUtility.xml	:warning:Warning	View	Details

xml/System.Net/WebUtility.xml

• Line 0, Column 0: [Warning: xref-not-found - See documentation] Cross reference not found: 'System.Uri.WebUtility.EscapeDataString*'.
• Line 0, Column 0: [Warning: xref-not-found - See documentation] Cross reference not found: 'System.Uri.WebUtility.EscapeDataString*'.

For more details, please refer to the build report.

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[learn-build-service-prod[bot]]

Learn Build status updates of commit 216c332:

:warning: Validation status: warnings

File	Status	Preview URL	Details
xml/System.Net/WebUtility.xml	:warning:Warning	View	Details

xml/System.Net/WebUtility.xml

• Line 0, Column 0: [Warning: xref-not-found - See documentation] Cross reference not found: 'System.Uri.WebUtility.EscapeDataString*'.
• Line 0, Column 0: [Warning: xref-not-found - See documentation] Cross reference not found: 'System.Net.WebUtility.UrlDecode'.
• Line 0, Column 0: [Warning: xref-not-found - See documentation] Cross reference not found: 'System.Uri.WebUtility.EscapeDataString*'.
• Line 0, Column 0: [Warning: xref-not-found - See documentation] Cross reference not found: 'System.Net.WebUtility.UrlDecodeToBytes'.

For more details, please refer to the build report.

Note: Your PR may contain errors or warnings or suggestions unrelated to the files you changed. This happens when external dependencies like GitHub alias, Microsoft alias, cross repo links are updated. Please use these instructions to resolve them.

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[learn-build-service-prod[bot]]

Learn Build status updates of commit 4c2ebf8:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
xml/System.Net/WebUtility.xml	:white_check_mark:Succeeded	View

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[MihaZupan]

Also the list of unescaped punction doesn't follow neither URI RFC (old or new) nor any other spec I could find.

https://github.com/dotnet/runtime/blob/770df102b0dfbf16c22ef64a270a989495cfe145/src/libraries/System.Private.CoreLib/src/System/Net/WebUtility.cs#L572

The code mentions https://datatracker.ietf.org/doc/html/rfc1738 that includes this bit:

safe           = "$" | "-" | "_" | "." | "+"
extra          = "!" | "*" | "'" | "(" | ")" | ","

but even that doesn't match the characters used 😄