feat(pack): add Pkl language support

lua/astrocommunity/pack/pkl/README.md

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+# Pkl Language Pack
+
+This plugin pack does the following:
+
+- Adds `pkl` Treesitter parser: <https://github.com/apple/tree-sitter-pkl>
+- Adds `pkl` language plugin: <https://github.com/apple/pkl-neovim>

lua/astrocommunity/pack/pkl/init.lua

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+return {
+  "https://github.com/apple/pkl-neovim",
+  dependencies = {
+    {
+      "nvim-treesitter/nvim-treesitter",
+      opts = function(_, opts)
+        local parser_config = require("nvim-treesitter.parsers").get_parser_configs()
+
+        parser_config.pkl = {
+          install_info = {
+            url = "https://github.com/apple/tree-sitter-pkl",
+            files = { "src/parser.c", "src/scanner.c" },
+            branch = "main",
+          },
+          filetype = "pkl",
+          used_by = { "pcf" },
+        }
+
+        opts.ensure_installed = require("astronvim.utils").list_insert_unique(opts.ensure_installed, "pkl")
+      end,
+    },
+  },
+  ft = "pkl",
+  init = function()
+    vim.filetype.add {
+      extension = {
+        pkl = "pkl",
+        pcf = "pkl",
+      },
+      filename = {
+        PklProject = "pkl",
+      },
+    }
+  end,
+}