STS -> MN: Escape "(c)" text to avoid render copyright symbol

[manuelfuenmayor]

In relation to https://github.com/metanorma/metanorma-bsi/issues/30

Whenever there is a (c) or (C), we need to escape it with a Zero Width Non Joiner character in order to avoid copyright symbol. By doing: (‌c).

For example, to avoid this situation from bs-en-12973:

**(b) Function analysis**

See <<sec_A.1.3>>.

**(c) Study of solution**

Study of solutions based on a cost-performance optimization, the constraints of the program being taken into account (use of term:[value,Value] Analysis/term:[value,Value] Engineering).

**(d) Monitoring objective costs**

Continuously monitored objective costs, to be expressed in inflation-adjusted currency units.

Output:

[Intelligent2013]

Fixed:

[manuelfuenmayor]

Fix confirmed, closing.