Create documentation on releasing new package version (#1443)

* Converting #1322 into a documentation

* Update and rename creating-new-package.md to creating-new-release.md

* Fix bold text

* Fix missed comment

Documentation/creating-new-release.md

+# Creating new .NET IoT release
+
+This is a list of steps which need to happen in order to release new version of .NET IoT.
+
+**This document is meant only for maintainers as special permissions might be required**
+
+## Steps
+
+- Step 1: Ensure all PRs meant for this release are merged.
+  - While the process is ongoing, make sure no new PRs get merged in order to ensure that the official build doesn't get reset.
+- Step 2: Regenerate device listing:
+  - `dotnet run` on https://github.com/dotnet/iot/tree/master/tools/device-listing
+  - Fix all warnings, re-run if needed to ensure no warnings.
+  - Always manually review the changes paying attention the generated document looks clear.
+  - Adjust categories/code of the generator if necessary.
+- Step 3: Create new package:
+  - Go to https://dev.azure.com/dnceng/internal/_build?definitionId=239
+  - Select "Run Pipeline", select row which says `variables` and add new one: `DotNetFinalVersionKind=release` (no quotes anywhere).
+  - Run and wait for it to finish.
+  - Once it is done and passes go to the artifacts section of the build, and find an artifact called 'Built packages' and from there download the two stable packages.
+  - Validate the package: double check version, check there are no unintentional changes.
+- Step 4: Manually push package to Nuget - as of writing this document only @joperezr has credentials
+- Step 5: Add git tag:
+  - Use `git tag -a <version> <commit_hash>` to locally create a tag.
+  - Use `git push origin <version>` to push it (`<version>` is i.e. `1.3`).
+- Step 6: Edit release notes on github:
+  - Follow example: https://github.com/dotnet/iot/releases/tag/1.2
+  - Copy the list of commits, clean those related to dependencies update.
+    - Use i.e.: https://github.com/dotnet/iot/compare/1.1...1.2 to see list of commits.
+  - Categorize them by: `System.Gpio`, `Iot.Device.Bindings`, `Other` changes.
+  - Rephrase/group them for consistency.
+  - Add the list of contributors ordered by the number of commits or alphabetically.
+- Step 7: After package is pushed to Nuget create a PR similar to https://github.com/dotnet/iot/pull/1310 to prepare for next release.
+- Step 8: Update dependencies on old version of the package:
+  - Option 1: Wait for `dependabot` to automatically create dependencies update PR (similar to: [System.Device.Gpio](https://github.com/dotnet/iot/pulls?q=is%3Apr+Bump+System.Device.Gpio+is%3Aclosed+author%3Aapp%2Fdependabot); [Iot.Device.Bindings](https://github.com/dotnet/iot/pulls?q=is%3Apr+Bump+Iot.Device.Bindings+is%3Aclosed+author%3Aapp%2Fdependabot))
+  - Options 2: Alternatively update versions manually to avoid swarm of PRs.
+    - See list of PRs created by bot in the last release, search for old version across the repo and create a single PR doing all these changes combined.
+- Step 9: Update the documentation:
+  - Link to repository: https://github.com/dotnet/iot-api-docs
+  - Currently this is not done by us, you will need to respond to the e-mail thread with request to update the documentation.
+    - E-mail thread title for reference: `System.Device.Gpio and Iot.Device.Bindings in the .NET API browser`.
+    - Contributors on the thread: @krwq @joperezr @richlander
+
+## TODO
+
+- Automate as much of this process as possible