feat: 导入 NMEA-0183 GPS 协议解析库（node-nmea）

NMEA-0183 语句解析器，含 21 个语句类型 codec 与配套单元测试。

- codecs/：APB/BWC/DBT/GGA/GLL/GRMT/GSA/GSV/HDG/HDM/HDT/MWV/RDID/
  RMB/RMC/ROT/RSA/TXT/VTG/VWR/ZDA
- test/：各 codec 对应的 mocha 用例
- .github/workflows/：node与 npm-publish 流水线

许可证：MIT（原作者 James Penn）

codecs/DBT.js

@@ -0,0 +1,45 @@
+var helpers = require("../helpers.js")
+
+/*
+ === DBT - Depth below transducer ===
+
+ ------------------------------------------------------------------------------
+ *******1   2 3   4 5   6 7
+ *******|   | |   | |   | |
+ $--DBT,x.x,f,x.x,M,x.x,F*hh<CR><LF>
+ ------------------------------------------------------------------------------
+
+ Field Number:
+
+ 1. Depth, feet
+ 2. f = feet
+ 3. Depth, meters
+ 4. M = meters
+ 5. Depth, Fathoms
+ 6. F = Fathoms
+ 7. Checksum
+ */
+
+exports.TYPE = 'depth-transducer';
+exports.ID = 'DBT';
+
+exports.decode = function(fields) {
+  return {
+    sentence: exports.ID,
+    type: exports.TYPE,
+    depthMeters: +fields[3],
+    depthFeet: +fields[1]
+  }
+}
+
+exports.encode = function (talker, msg) {
+  var result = ['$' + talker + exports.ID];
+  result.push(helpers.encodeFixed(msg.depthFeet,2));
+  result.push('f');
+  result.push(helpers.encodeFixed(msg.depthMeters, 2));
+  result.push('M');
+  result.push(helpers.encodeFixed(msg.depthFathoms, 2));
+  result.push('F');
+  var resultMsg = result.join(',');
+  return resultMsg + helpers.computeChecksum(resultMsg);
+}