move windows_x86_64 to Tier 1

Author: aignas

docs/support.md

@@ -45,14 +45,17 @@ is Linux, Mac, and Windows.
 
 In order to better describe different support levels, the below acts as a rough
 guideline for different platform tiers:
-* Tier 0 - The platforms that our CI runs: `linux_x86_64`, `osx_x86_64`, `windows_x86_64`, `RBE linux_x86_64`.
-* Tier 1 - The platforms that are similar enough to what the CI runs: `linux_aarch64`, `osx_aarch64`.
-* Tier 2 - The rest.
+* Tier 0 - The platforms that our CI runs: `linux_x86_64`, `osx_x86_64`, `RBE linux_x86_64`.
+* Tier 1 - The platforms that are similar enough to what the CI runs: `linux_aarch64`, `osx_arm64`.
+  What is more, `windows_x86_64` is in this list as we run tests in CI but
+  developing for Windows is more challenging and features may come later to
+  this platform.
+* Tier 2 - The rest of the platforms that may have varying level of support, e.g.
+  `linux_s390x`, `linux_ppc64le`, `windows_arm64`.
 
 :::{note}
-Code to support other platforms is allowed, but regressions will be fixed on a
-best-effort basis. Feel free to contribute code that fixes `rules_python` on
-a Tier 2 platform.
+Code to support Tier 2 platforms is allowed, but regressions will be fixed on a
+best-effort basis, so feel free to contribute by creating PRs.
 
 If you would like to provide/sponsor CI setup for a platform that is not Tier 0,
 please create a ticket or contact the maintainers on Slack.