feat: add support for pruner formatter (#856)

* Add support for pruner formatter

* doc: unify metadata format

---------

Co-authored-by: Steven Arcangeli <506791+stevearc@users.noreply.github.com>

Author: julienvincent

lua/conform/formatters/pruner.lua

@@ -0,0 +1,26 @@
+---@type conform.FileFormatterConfig
+return {
+  meta = {
+    url = "https://github.com/pruner-formatter/pruner",
+    description = "A language-agnostic, treesitter powered formatter.",
+  },
+  command = "pruner",
+  args = function(_, ctx)
+    local args = { "format" }
+
+    local textwidth = vim.api.nvim_get_option_value("textwidth", {
+      buf = ctx.buf,
+    })
+    if textwidth and textwidth > 0 then
+      table.insert(args, "--print-width=" .. textwidth)
+    end
+
+    local filetype = vim.api.nvim_get_option_value("filetype", {
+      buf = ctx.buf,
+    })
+    table.insert(args, "--lang=" .. filetype)
+
+    return args
+  end,
+  stdin = true,
+}