Switch clipper to polyclip-ts

(closes #67)

Also update node engine and ci to Node 18+
Node 16.x is end-of-life

.github/workflows/build.yml

@@ -15,7 +15,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [16.14, 18, 20]
+        node-version: [18, 20]
 
     steps:
     - uses: actions/checkout@v3

index.mjs

@@ -1,8 +1,8 @@
 import * as CountryCoder from '@rapideditor/country-coder';
+import * as Polyclip from 'polyclip-ts';
 
 import calcArea from '@mapbox/geojson-area';
 import circleToPolygon  from 'circle-to-polygon';
-import polygonClipping from 'polygon-clipping';
 import precision  from 'geojson-precision';
 import prettyStringify from '@aitodotai/json-stringify-pretty-compact';
 
@@ -345,11 +345,11 @@ export default class {
 }
 
 
-// Wrap the mfogel/polygon-clipping library and return a GeoJSON feature.
+// Wrap the https://github.com/luizbarboza/polyclip-ts library and return a GeoJSON feature.
 function _clip(features, which) {
   if (!Array.isArray(features) || !features.length) return null;
 
-  const fn = { UNION: polygonClipping.union, DIFFERENCE: polygonClipping.difference }[which];
+  const fn = { UNION: Polyclip.union, DIFFERENCE: Polyclip.difference }[which];
   const args = features.map(feature => feature.geometry.coordinates);
   const coords = fn.apply(null, args);
   return {

package.json

@@ -43,12 +43,12 @@
     "@rapideditor/country-coder": "^5.2.1",
     "circle-to-polygon": "^2.2.0",
     "geojson-precision": "^1.0.0",
-    "polygon-clipping": "~0.15.3"
+    "polyclip-ts": "~0.16.3"
   },
   "devDependencies": {
     "c8": "^8.0.1",
-    "esbuild": "^0.19.2",
-    "eslint": "^8.48.0",
+    "esbuild": "^0.19.3",
+    "eslint": "^8.49.0",
     "npm-run-all": "^4.1.5",
     "shx": "^0.3.4",
     "tap": "^16.3.8"
@@ -57,6 +57,6 @@
     "access": "public"
   },
   "engines": {
-    "node": ">=16.14.0"
+    "node": ">=18"
   }
 }