Add license check workflow

This adds the Apache License Eye github action and necessary
configuraiton. It will now ensure that all files contain a valid SPDX
header.

Fixes: #201

Signed-off-by: Dave Tucker <[email protected]>

Author: dave-tucker

src/nflog/message.rs

@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 use crate::{
     buffer::NetfilterBuffer,
     constants::{NFNL_SUBSYS_ULOG, NFULNL_MSG_CONFIG, NFULNL_MSG_PACKET},

src/nflog/nlas/config/nla.rs

@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 use anyhow::Context;
 use byteorder::{BigEndian, ByteOrder};
 use derive_more::{From, IsVariant};

src/nflog/nlas/mod.rs

@@ -1,2 +1,4 @@
+// SPDX-License-Identifier: MIT
+
 pub mod config;
 pub mod packet;

src/nflog/nlas/packet/mod.rs

@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: MIT
+
 mod hw_addr;
 mod nla;
 mod packet_hdr;