Self_tokens: add semi-colon before export and namespace

type:fixed

For LIGO developers

As reported in #1364 (closed), semi-colon is needed before export keyword. JsLIGO adds semi-colons automatically during a "self-tokens pass". This MR modifies the pass to account for export and namespace.

Closes #1364 (closed) .

Changelog details:
JsLIGO: semi-colons are automatically added before the export and namespace keywords.