Extension Header Option Length Is Single Byte

[hawkinsw]

The L in the extension header option TLV is a single byte.

(Also, fix minor typo in comment.)

[hawkinsw]

Thank you so much for your work on this library. It is just the tool set I need for my current side project. I hope that this little fix helps.

(And, if I have read RFC8200 wrong, please correct me!)

[hawkinsw]

Hope that this little fix is helpful! If there is anything I can do to clean it up and make it easier for you to incorporate, I would be more than happy to make those changes! Again, thank you for all the work you have done on this library/toolkit!

Also, I should say, the way the code currently is, there would be change to the contents of the packet (because the padding is 0x00 and skipping that additional byte simply leaves a 0x00). However, I had a few PRs that I thought I could offer (that helped me when using the tool) that would really benefit from having this little bit fixed. Sorry for not being clearer earlier!