Update manuscripts tutorial with inline code syntax

[cwickham]

• JupyterLab and VS Code link out, but could now include an example of {python} syntax.
• RStudio has example of r syntax which could be updated to use {r}.

Also need to change files in the respective template repos

[cwickham]

Decided against using inline code in the JupyterLab edition, since it introduces complications around execution (e.g. currently no execution is required, adding inline code will require execution).