Support Visual Studio about contextive

[chrissimon-au]

Initial poc tests with https://learn.microsoft.com/en-us/visualstudio/extensibility/adding-an-lsp-extension?view=vs-2022 suggest that the default LSP client may not be ideal:

From that page, In fact, support for LSP language servers is designed to work only in open folder/file scenarios. - we want Contextive to 'overlay' information supplied even when VS is used to open a solution or a project, not just the 'open folder' scenario.

May need to investigate using the OmniSharp language client and explicitly wiring up default handles, (e.g. see QuickInfo tooltip - https://learn.microsoft.com/en-us/visualstudio/extensibility/walkthrough-displaying-quickinfo-tooltips?view=vs-2022&tabs=csharp) into the language client call to the language server.