Add ability to convert URLs to clickable HyperLinks

[augustoproiete]

Discussed in https://github.com/serilog-contrib/serilog-sinks-richtextbox/issues/11#issuecomment-912642600

^{Originally posted by TonyValenti September 3, 2021} If a URL is logged, please convert it to a clickable HyperLink

[augustoproiete]

Some initial thoughts:

• Enabled by default with option to turn off, or Disabled by default with option to turn on?
• Should URLs in message templates be automatically converted to hyperlinks? e.g. Log.Information("Site: https://serilog.net")?
• Should URLs in properties be automatically converted to hyperlinks? e.g. Log.Information("Site: {url}", "https://serilog.net")?
• Should we create a new format type where the user can opt-in to formatting as hyperlink? e.g. Log.Information("Site: {url:hyperlink}", "https://serilog.net")?
• Depending on the answers above, should we scan every log message _after rendering and perform the conversion, or should we inspect message template and properties separately?
• Should we also scan for email addresses and convert to a hyperlink with mailto:?
• Should we also scan for file paths and convert to a hyperlink with file://?
• What would be a good interface to allow users to apply a custom logic to detect/replace hyperlinks (intercept or passthrough)?