Add metadatas

[johnfercher]

Description

• Add metadatas
• https://maroto.io/#/v2/features/metadatas?id=metadatas

Related Issue

Checklist

check with "x", if applied to your change

• All methods associated with structs has func (s *struct) method() {} name style.
• Wrote unit tests for new/changed features.
• Updated docs/doc.go
• Updated pkg/pdf/example_test.go
• Updated README.md
• Updated all examples inside internal/examples
• New public methods/structs/interfaces has comments upside them explaining they responsibilities
• Executed make dod with none issues pointed out by golangci-lint and goreportcard-cli

[codecov]

Codecov Report

Patch coverage: 5.41% and project coverage change: -0.88% ⚠️

Comparison is base (62bfbd8) 27.12% compared to head (40e64d5) 26.24%.

Additional details and impacted files

@@            Coverage Diff             @@
##               v2     #306      +/-   ##
==========================================
- Coverage   27.12%   26.24%   -0.88%     
==========================================
  Files          17       17              
  Lines         815      850      +35     
==========================================
+ Hits          221      223       +2     
- Misses        589      622      +33     
  Partials        5        5              

Flag	Coverage Δ
unittests	26.24% <5.41%> (-0.88%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
pkg/maroto.go	12.97% <0.00%> (ø)
pkg/config/builder.go	66.26% <5.72%> (-16.55%)	⬇️

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