fix(ifc-splitter): add IFCMECHANICALFASTENER to elements types

[ShaMan123]

Description

related #174

Adds IFCMECHANICALFASTENER to ELEMENT_TYPES so that it is included in the output ifc. This fixes the style of the output IFCMECHANICALFASTENER

Additional context

#174 (comment)

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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