.mapping was chosen as the extension for single Enigma files too (see Discord)
ExtensionFileChooser was written to be a bit more general than this PR needs it to be so that it can be used for e.g. the open JAR dialog in the future.
Also fixes #533 by choosing Enigma directories as the default save format when closing.
Some notes about the extension choices:
.txtfor ProGuard comes from the ReTrace manual: "java -jar retrace.jar mapping.txt stacktrace.txt".txtfor Recaf mappings comes from Recaf's test code.mappingwas chosen as the extension for single Enigma files too (see Discord)ExtensionFileChooserwas written to be a bit more general than this PR needs it to be so that it can be used for e.g. the open JAR dialog in the future.Also fixes #533 by choosing Enigma directories as the default save format when closing.