Do not require strict spec adherence

[loraderon]

Prerequisites

• I have written a descriptive pull-request title
• I have verified that there are no overlapping pull-requests open
• I have verified that I am following matches the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules 👮.
• I have provided test coverage for my change (where applicable)

Description

No longer throws InvalidFontFileException for invalid subTables.

Closes #269

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #277 (a97cdf9) into main (cb8a60c) will increase coverage by 0%.
The diff coverage is 5%.

@@          Coverage Diff          @@
##            main    #277   +/-   ##
=====================================
  Coverage     81%     82%           
=====================================
  Files        216     216           
  Lines      11264   11260    -4     
  Branches    1750    1750           
=====================================
+ Hits        9233    9238    +5     
+ Misses      1607    1599    -8     
+ Partials     424     423    -1     

Flag	Coverage Δ
unittests	82% <5%> (+<1%)	⬆️

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

Impacted Files	Coverage Δ
...es/AdvancedTypographic/GPos/LookupType1SubTable.cs	82% <0%> (+1%)	⬆️
...es/AdvancedTypographic/GPos/LookupType2SubTable.cs	97% <0%> (+<1%)	⬆️
...es/AdvancedTypographic/GPos/LookupType3SubTable.cs	59% <0%> (+<1%)	⬆️
...es/AdvancedTypographic/GPos/LookupType4SubTable.cs	90% <0%> (ø)
...es/AdvancedTypographic/GPos/LookupType5SubTable.cs	89% <0%> (ø)
...es/AdvancedTypographic/GPos/LookupType6SubTable.cs	74% <0%> (ø)
...es/AdvancedTypographic/GPos/LookupType7SubTable.cs	80% <0%> (+<1%)	⬆️
...es/AdvancedTypographic/GPos/LookupType8SubTable.cs	79% <0%> (ø)
...es/AdvancedTypographic/GPos/LookupType9SubTable.cs	66% <0%> (ø)
...Tables/AdvancedTypographic/GSub/LookupListTable.cs	90% <0%> (ø)
... and 10 more

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[JimBobSquarePants]

Fantastic. Thanks!