Add default impl for IpAuthHeader and Ipv6RawExtHeader #67

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (4b6e0b6) 99.29% compared to head (946b6ce) 99.29%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #72 +/- ## ======================================= Coverage 99.29% 99.29% ======================================= Files 142 142 Lines 35230 35264 +34 ======================================= + Hits 34980 35015 +35 + Misses 250 249 -1 ``` | [Impacted Files](https://app.codecov.io/gh/JulianSchmid/etherparse/pull/72?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Julian+Schmid) | Coverage Δ | | |---|---|---| | [etherparse/src/internet/ip\_auth\_header.rs](https://app.codecov.io/gh/JulianSchmid/etherparse/pull/72?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Julian+Schmid#diff-ZXRoZXJwYXJzZS9zcmMvaW50ZXJuZXQvaXBfYXV0aF9oZWFkZXIucnM=) | `100.00% <100.00%> (ø)` | | | [etherparse/src/internet/ipv6\_raw\_ext\_header.rs](https://app.codecov.io/gh/JulianSchmid/etherparse/pull/72?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Julian+Schmid#diff-ZXRoZXJwYXJzZS9zcmMvaW50ZXJuZXQvaXB2Nl9yYXdfZXh0X2hlYWRlci5ycw==) | `100.00% <100.00%> (ø)` | | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/JulianSchmid/etherparse/pull/72/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Julian+Schmid)

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