Remove support for Node 12

Closes GH-70.
Related-to GH-69.

.github/workflows/main.yml

@@ -7,15 +7,15 @@ jobs:
     name: ${{matrix.node}}
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: dcodeIO/setup-node-nvm@master
         with:
           node-version: ${{matrix.node}}
       - run: npm install
       - run: npm test
-      - uses: codecov/codecov-action@v1
+      - uses: codecov/codecov-action@v3
     strategy:
       matrix:
         node:
-          - lts/erbium
-          - node
+          - lts/fermium
+          - lts/gallium

readme.md

@@ -61,7 +61,7 @@ This plugin does not check external URLs (see
 ## Install
 
 This package is [ESM only](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c).
-In Node.js (version 12.20+, 14.14+, or 16.0+), install with [npm][]:
+In Node.js (version 14.14+, or 16.0+), install with [npm][]:
 
 ```sh
 npm install remark-validate-links
@@ -315,7 +315,7 @@ corresponding option.
 
 Projects maintained by the unified collective are compatible with all maintained
 versions of Node.js.
-As of now, that is Node.js 12.20+, 14.14+, and 16.0+.
+As of now, that is Node.js 14.14+, and 16.0+.
 Our projects sometimes work with older versions, but this is not guaranteed.
 
 This plugin works with `unified` version 6+, `remark` version 7+, and