Bugfix: Handle TypedArrays and Buffers in deep-merge/clone

[ykw9263]

What kind of change does this PR introduce?
This fixes a bug mentioned in #1743 where providing font buffers crashes table generation.

In lib\table\utils.js, deepMerge and deepClone() copy properties key by key including Buffer and Uint8Array without inheriting the class. This causes the merged font buffer failing to be recognised by PDFFontFactory which relies on instanceof to determine the type of font sources.

This PR changes the behaviour of deepMerge() and deepClone() to clone TypedArrays and Buffers using .slice() and Buffer.from(buffer) respectively.

Additional unit tests (fonts in tables, deep-merging buffers) are added for the changes.

Checklist:

• Unit Tests
• Documentation
• Update CHANGELOG.md
• Ready to be merged

TODO:

• ArrayBuffer may also need to be handled the same way
• Fonts buffer is not likely to be tampered and copying by reference may be more suitable.
• table fonts are deep merges at:

  • pdfkit/lib/table/style.js

    Line 118 in 2fdafa2

    colStyle = deepMerge(defaultColStyle, colStyle);

  • pdfkit/lib/table/style.js

    Line 62 in 2fdafa2

    rowStyle = deepMerge(defaultRowStyle, rowStyle);

  • pdfkit/lib/table/normalize.js

    Line 96 in 2fdafa2

    const font = deepMerge({}, colStyle.font, rowStyle.font, cell.font);

[blikblum]

Where deepClone is called in this code path?

I would like to avoid cloning buffer / UintArray in name of efficiency

[blikblum]

AFAIK we only support Uint8Array