refactor lang to constants

lua/cp/constants.lua

@@ -0,0 +1,24 @@
+local M = {}
+
+M.PLATFORMS = { "atcoder", "codeforces", "cses" }
+M.ACTIONS = { "run", "debug", "test", "next", "prev" }
+
+M.CPP = "cpp"
+M.PYTHON = "python"
+
+---@type table<string, string>
+M.filetype_to_language = {
+	cc = M.CPP,
+	cxx = M.CPP,
+	cpp = M.CPP,
+	py = M.PYTHON,
+	py3 = M.PYTHON,
+}
+
+---@type table<string, string>
+M.canonical_filetypes = {
+	[M.CPP] = "cpp",
+	[M.PYTHON] = "python",
+}
+
+return M