Update documentation for latest versions

I'm the main maintainer on the OpenXML SDK and would like to get the docs updated to reflect the current state of things. This issue will be a (potentially growing) list of the items that we would like to update:

• The documentation refers to specific versions - this is unnecessary as the version is not static nor is the content dependent on it (https://github.com/OfficeDev/open-xml-docs/pull/158)
• APIs have not been updated since 2.8.1 - should add APIs for at least v2.2.0 and v3.0.0 (it'll be released next month) (#156)
• New samples are available at https://github.com/dotnet/Open-XML-SDK/tree/main/samples and should be migrated here
  • AnimatedModel3DExample
  • DocumentTaskExample
  • IsolatedStorageExceptionWorkaround
  • Linq
  • NamedSheetView
  • PowerPointModernCommentSample
  • RichData
  • SunburstChartExample
  • SVGExample
  • ThreadedCommentExample
• Samples use VB and CS but are all inline and should be moved to actual test projects, be runnable, and shown in docfx tabs #163
• Updated/new topics:
  • IFeatureCollection usage https://github.com/OfficeDev/open-xml-docs/pull/179
  • LINQ support
  • Migration to v3 https://github.com/OfficeDev/open-xml-docs/pull/178
• Update getting started related steps (no longer need to "install" SDK - update to account for NuGet packages and dotnet CLI) https://github.com/OfficeDev/open-xml-docs/pull/171
• Reorganize doc file structure so that they match the toc https://github.com/OfficeDev/open-xml-docs/pull/169
• references to ISO/IEC 29500:2008 should be updated to 2016, including one reference to ISO/IEC2900:2008 (missing "5")
• there are references and procedures for Visual Studio 2008
• remove references to the SDK 1.0
• completely revamp the What's New in the Open XML SDK topic https://github.com/OfficeDev/open-xml-docs/pull/172
• Documentation section in SDK Readme still mentions SDK 2.5
• Fix broken samples
  • #146
  • #144
  • #91
  • #56
  • #53
  • #51
  • #153