vlib: add toml module + tests (#11964)

vlib/toml/ast/ast.v

@@ -0,0 +1,28 @@
+// Copyright (c) 2021 Lars Pontoppidan. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+module ast
+
+import toml.input
+
+// Root represents the root structure of any parsed TOML text snippet or file.
+[heap]
+pub struct Root {
+pub:
+	input input.Config // User input configuration
+pub mut:
+	table Node
+	// errors           []errors.Error    // all the checker errors in the file
+}
+
+pub fn (r Root) str() string {
+	mut s := typeof(r).name + '{\n'
+	s += '  input:  $r.input\n'
+	s += '  table:  $r.table\n'
+	s += '}'
+	return s
+}
+
+pub fn (r Root) to_json() string {
+	return r.table.to_json()
+}