Updated Elasticsearch.Net ver. 7.4.2 to fix performance issue

[snakefoot]

See also: https://github.com/elastic/elasticsearch-net/releases/tag/7.4.2

Checklist

• [X] My commits follow Conventional Commits
• [X] documentation is updated

Other Changes

• Enabled GenerateDocumentationFile and fixed warnings
• Added https://www.nuget.org/packages/Microsoft.SourceLink.GitHub
• Updated NLog + Newtonsoft.Json

[snakefoot]

@markmcdowell Possible to get a nuget-release as a late christmas present?

[markmcdowell]

Sorry yes, I’ll do a release tonight