Blazor 'integrity.ps1' script security

[guardrex]

Addresses #19286

Courtesy ping for @blowdart 🎯 ... I'm working with Blazor security subject matter here. 😨😄

Internal Review Topic (links to section, See NOTE)

• Multiple users have hit this problem where a heuristic scanner throws a false positive.
• Not going to go with an INCLUDE for now. This is the only spot in Blazor docs that we need to cover this at this time. [Note tho that this is a wider problem across the repo, i.e. ... non-Blazor scenarios.]
• Explains that an exception is required for the file, BUT calls out a strong warning on file security when creating exceptions AND briefly covers performing a checksum comparison ....... and calls out that even that doesn't guarantee 100% safety.

[mkArtakMSFT]

Thanks @guardrex !

[guardrex]

@HaoK ... See if I went too far 😅 with the NOTE and/or phrased it well. I don't want to leave devs hanging, but I don't want to get too deep in the weeds either .... and checksums aren't an iron-clad guarantee anyway.

[HaoK]

Looks good as usual @guardrex !