fix(kumascript): improve MacroInvocationError display

[caugner]

Summary

Fixes #7106 by improving the way MacroInvocationErrors are displayed (both in the command line and in the browser).

Problem

Macro errors were always confusing and hard to locate, because the shown line number did not correspond to the Markdown file.

Solution

Remove the line numbers in favor of showing the source context (+/- 2 lines).

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Screenshots

Before

After

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How did you test this change?

Opened http://localhost:3000/en-US/docs/MDN/Kitchensink locally and introduced a syntax error in my local mdn/content checkout by removing the second " in this line:

https://github.com/mdn/content/blob/6fdcfb2bb5862d89d84cc511cf31a0e4fffc72bf/files/en-us/mdn/kitchensink/index.md?plain=1#L300

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