chore: Include support for node-18

This adds `node-18` to the testing matrix and verifies that all tests
still work (no breaking changes to stream functionality).

Fixes: #32

.nvmrc

@@ -1 +1 @@
-16.14.2
+18.0.0

Jenkinsfile

@@ -48,7 +48,7 @@ pipeline {
         axes {
           axis {
             name 'NODE_VERSION'
-            values '12', '14', '16', '17'
+            values '12', '14', '16', '18'
           }
         }
 
@@ -97,7 +97,7 @@ pipeline {
       agent {
         docker {
           label 'ec2-fleet'
-          image "us.gcr.io/logdna-k8s/node:16-ci"
+          image "us.gcr.io/logdna-k8s/node:18-ci"
           customWorkspace "${PROJECT_NAME}-${BUILD_NUMBER}"
         }
       }
@@ -129,7 +129,7 @@ pipeline {
       agent {
         docker {
           label 'ec2-fleet'
-          image "us.gcr.io/logdna-k8s/node:16-ci"
+          image "us.gcr.io/logdna-k8s/node:18-ci"
           customWorkspace "${PROJECT_NAME}-${BUILD_NUMBER}"
         }
       }

README.md

@@ -53,6 +53,14 @@ in Node.js could also benefit from using this.
 npm install @logdna/tail-file
 ```
 
+## Supported Versions of Node.js
+This package works with the following *supported* versions.  Other versions might work, but the ones listed here are officially tested.
+If backward-compatibility is lost over time, a `major` version will be released supporting
+the latest version, and deprecating incompatible versions. Users are then encouraged to try
+previous versions of this package for those deprecated versions of Node.js.
+
+**Node.js versions**: `12`, `14`, `16`, `18`
+
 ## Usage
 
 Instantiate an instance by passing the full path of a file to tail.