Parse files that end without a newline or semicolon

See alex-pinkus#166

```
$ echo -n "print(3)" > nonewline.swift
$ npx tree-sitter parse nonewline.swift # No parse error
```

grammar.js

@@ -222,7 +222,13 @@ module.exports = grammar({
  source_file: ($) =>
  seq(
  optional($.shebang_line),
- repeat(seq($._top_level_statement, $._semi))
+ optional(
+ seq(
+ $._top_level_statement,
+ repeat(seq($._semi, $._top_level_statement)),
+ optional($._semi)
+ )
+ )
  ),
  shebang_line: ($) => seq("#!", /[^\r\n]*/),
  ////////////////////////////////