chore: some more htmltest fixes

[jmeridth]

• added a website that redirects to ignore list
• change .net tags to dotnet, less complications

[Copilot]

Pull request overview

This PR updates site content and htmltest configuration to reduce link-check noise and normalize post tagging for .NET-related posts.

Changes:

• Replace legacy ".net" tags with dotnet in affected post front matter.
• Add vim.wikia.com to .htmltest.yml IgnoreURLs to suppress failures caused by redirects.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
content/posts/2012-04-12-nuget-dependency-versioning-and-log4net-1.2.11.md	Normalize .net tag to dotnet in front matter.
content/posts/2012-03-23-how-to-capture-exception-message-from-assert-throws-in-nunit.md	Normalize .net tag to dotnet in front matter.
content/posts/2011-06-04-opportunity.md	Normalize .net tag to dotnet in front matter.
.htmltest.yml	Ignore vim.wikia.com to avoid htmltest failures due to redirects.

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