do not process [square brackets] unless followed by (round brackets)

[sujato]

In the Github actions nilakkhana transformation, we convert a reference in a markdown link form []() or else just a standard markdown link.

However this transformation is being triggered when there is a simple use of [square brackets] in a comment, creating bugs in the output.

The transformation should only be triggered when the [square brackets](are immediately followed by round brackets). When [square brackets] appear alone in a text they should not be touched.

[ihongda]

Bhante, I have checked and tested the related code, and it seems to be ok at the moment.

https://github.com/suttacentral/bilara-data/blob/published/comment/en/sujato/sutta/mn/mn35_comment-en-sujato.json