posh: add page (#22795)

Co-authored-by: Managor <42655600+Managor@users.noreply.github.com>
Co-authored-by: Ivan Baluta <ivanbaluta.dev@gmail.com>

pages/common/posh.md

@@ -0,0 +1,28 @@
+# posh
+
+> Gems documentation browser for Ruby developers.
+> More information: <https://poshtui.com/docs>.
+
+- Download documentation to your machine (run inside a Ruby project) and print full sync report:
+
+`posh sync --full`
+
+- Start the interactive documentation browser for the current project:
+
+`posh`
+
+- Clear all docsets from your machine:
+
+`posh clear`
+
+- Generate the autocompletion script for your shell:
+
+`posh completion {{bash|fish|powershell|zsh}}`
+
+- Display help:
+
+`posh {{[-h|--help]}}`
+
+- Display help for a specific subcommand:
+
+`posh {{subcommand}} {{[-h|--help]}}`