Allow different types of escapes in template output

To allow exact code to be generated in different scenarios, we should provide different kinds of escapes for templates to choose. Here is a tentative list of escapes we need:

- HTML escape ( now available as ``{{tag}}`` )
- No escape ( now available as ``{{{tag}}}`` )
- Backslash escape (there are two variants: JS and commonmark).
JS string escape appears to be used in quotes inside Nunjucks tags (verification still to be done).
The most noted difference of the escapes are about whether to escape "\n".
AsciiDoctor appears to have backslash escape that "aren't very reliable" (words quoted from section 12.5 of Asciidoctor user manual). I guess commonmark escapes do well there.

- URI escape (for use in ``)

Comece localizando o tratamento existente da saída de templates que fornece as formas atuais de HTML e sem escape. Verifique como o escape de strings JavaScript é usado dentro de tags Nunjucks e, em seguida, compare os comportamentos necessários de JavaScript, CommonMark e URI. O trabalho estará concluído quando os templates puderem escolher cada modo de escape acordado e os casos documentados produzirem exatamente a saída esperada.

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