feat(pack): Add Scala language pack (#501)

lua/astrocommunity/pack/scala/README.md

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+# Scala Language Pack
+
+Requires:
+
+- `metals` or `coursier` in your path
+
+This plugin pack does the following:
+
+- Adds `scala` treesitter parsers
+- Adds `metals` language server
+- Adds debugger for scala to `nvim-dap`
+- Adds [nvim-metals](https://github.com/scalameta/nvim-metals) for language specific tooling

lua/astrocommunity/pack/scala/init.lua

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+local utils = require "astronvim.utils"
+
+return {
+  {
+    "nvim-treesitter/nvim-treesitter",
+    opts = function(_, opts)
+      if opts.ensure_installed ~= "all" then
+        opts.ensure_installed = utils.list_insert_unique(opts.ensure_installed, "scala")
+      end
+    end,
+  },
+  {
+    "scalameta/nvim-metals",
+    init = function()
+      astronvim.lsp.skip_setup = utils.list_insert_unique(astronvim.lsp.skip_setup, "metals")
+      vim.api.nvim_create_autocmd("FileType", {
+        pattern = { "scala", "sbt" },
+        callback = function()
+          if vim.fn.executable "metals" ~= 1 and vim.fn.executable "coursier" ~= 1 then
+            vim.notify "`metals` or `coursier` are required to be installed for `nvim-metals` to work."
+            return
+          end
+
+          local metals = require "metals"
+
+          local user_config = require("astronvim.utils.lsp").config "metals"
+          local old_on_attach = user_config.on_attach
+          user_config.on_attach = function(...)
+            old_on_attach(...)
+            metals.setup_dap()
+          end
+
+          metals.initialize_or_attach(utils.extend_tbl(metals.bare_config(), user_config))
+        end,
+        group = vim.api.nvim_create_augroup("nvim-metals", { clear = true }),
+      })
+    end,
+  },
+  {
+    "mfussenegger/nvim-dap",
+    optional = true,
+    config = function()
+      local scala_config = {
+        {
+          type = "scala",
+          request = "launch",
+          name = "RunOrTest",
+          metals = {
+            runType = "runOrTestFile",
+          },
+        },
+        {
+          type = "scala",
+          request = "launch",
+          name = "Test Target",
+          metals = {
+            runType = "testTarget",
+          },
+        },
+      }
+      local dap = require "dap"
+      dap.configurations.scala = dap.configurations.scala and vim.list_extend(dap.configurations.scala, scala_config)
+        or scala_config
+    end,
+  },
+}