Remove support for Node.js version 12, add 18

- 2022-04-19: [v18 released](https://nodejs.org/en/about/releases/).
- 2022-04-30: [v12 went from LTS to end-of-life status](https://github.com/nodejs/Release#end-of-life-releases).

Also, sync the npm versions which correspond to Node.js v14/v16/v18 per https://nodejs.org/en/download/releases/.

.github/workflows/ci.yaml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: [12, 14, 16]
+        node: [14, 16, 18]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-node@v2
@@ -23,7 +23,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: [12, 14, 16]
+        node: [14, 16, 18]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-node@v2
@@ -36,7 +36,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: [12, 14, 16]
+        node: [14, 16, 18]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-node@v2
@@ -49,7 +49,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: [12, 14, 16]
+        node: [14, 16, 18]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-node@v2
@@ -61,7 +61,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: [12, 14, 16]
+        node: [14, 16, 18]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-node@v2

package.json

@@ -7,8 +7,8 @@
   "repository": "github:nextstrain/auspice",
   "homepage": "https://www.npmjs.com/package/auspice",
   "engines": {
-    "node": "^12 || ^14 || ^16",
-    "npm": ">=6.9"
+    "node": "^14 || ^16 || ^18",
+    "npm": "^6.14.4 || ^7.10.0 || ^8.6.0"
   },
   "bin": {
     "auspice": "./auspice.js"