Stop testing Node v10/v12 in CI (both EOL)

They still work fine, but they may stop working in future. This
library supports all maintained Node releases, but will stop actively
supporting unmaintained releases approximately a year after they hit
end-of-life. This only affects usage within Node.js itself.

Author: pimterry

.github/workflows/ci.yml

@@ -7,7 +7,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [10.x, 12.x, 14.x, 16.x, v16.16.0, 18.x, '*']
+        node-version: [14.x, 16.x, v16.16.0, 18.x, '*']
 
     steps:
       - uses: actions/checkout@v2