Implement AddSubtable method for the Table component

[adrg]

Add ability to copy a table onto another table, at a specified position.
Addresses #395

[codecov]

Codecov Report

Merging #400 into v3 will decrease coverage by 5.35%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##               v3     #400      +/-   ##
==========================================
- Coverage   60.77%   55.42%   -5.36%     
==========================================
  Files         151      151              
  Lines       27438    27464      +26     
==========================================
- Hits        16676    15222    -1454     
- Misses      10378    10380       +2     
- Partials      384     1862    +1478

Impacted Files	Coverage Δ
pdf/creator/table.go	86.68% <100%> (-2.13%)	⬇️
pdf/creator/utils.go	55.55% <0%> (-22.23%)	⬇️
pdf/core/security/handlers.go	33.33% <0%> (-16.67%)	⬇️
pdf/model/optimize/image_ppi.go	59.7% <0%> (-16.42%)	⬇️
pdf/model/reader.go	48.34% <0%> (-15.17%)	⬇️
pdf/ps/exec.go	62.96% <0%> (-14.82%)	⬇️
pdf/ps/operations.go	53.45% <0%> (-13.84%)	⬇️
pdf/model/signature_handler.go	55.04% <0%> (-13.77%)	⬇️
pdf/core/stream.go	31.08% <0%> (-13.52%)	⬇️
pdf/extractor/image.go	66.08% <0%> (-13.05%)	⬇️
... and 94 more

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