Added tag support for including tags in the exceptionless feed

[dnoakes]

Example usage,

Serilog: Log.ForContext("Tags", new List() { "Tag1", "Tag2"}).Information("Seri info");
ILogger:
using (var scope = _logger.BeginScope(new Dictionary<string, object> { ["Tags"] = new string[] { "Test1", "Test2" }}))
{
_logger.Log(logLevel, eventId, state, exception, formatter);
}

[CLAassistant]

All committers have signed the CLA.

[niemyjski]

Thanks for the PR! I've left a comment on the tags implementation. I wonder if it's worth supporting other first-class properties like value as well.

[niemyjski]

Thanks again for the PR. I just published https://github.com/exceptionless/serilog-sinks-exceptionless/releases/tag/v5.0.0