compile_asn1_subdir: filter compiled files by .asn suffix

When I open the .asn file in vim, pySim should not attempt to read the
vim .swp file as asn.1.

	  File "/home/moi/osmo-dev/src/pysim/pySim/esim/saip/__init__.py", line 45, in <module>
	    asn1 = compile_asn1_subdir('saip')
	[...]
	  File "<frozen codecs>", line 325, in decode
	UnicodeDecodeError: 'utf-8' codec can't decode byte 0xad in position 21: invalid start byte

Related: OS#6937
Change-Id: I37df3fc081e51e2ed2198876c63f6e68ecc8fcd8

pySim/esim/__init__.py

@@ -54,6 +54,8 @@ def compile_asn1_subdir(subdir_name:str, codec='der'):
     __ver = sys.version_info
     if (__ver.major, __ver.minor) >= (3, 9):
         for i in resources.files('pySim.esim').joinpath('asn1').joinpath(subdir_name).iterdir():
+            if not i.name.endswith('.asn'):
+                continue
             asn_txt += i.read_text()
             asn_txt += "\n"
     #else: