Build: Replace grunt-git-authors dependency with simple git-log command

I considered using git-shortlog as
`git shortlog -se --format='%aE' --no-merges`, which indeed gets us
fairly close. But, the available sort options there (as of git 2.41.0)
are by name or by count, not by first appearance.

So, instead, use git log, and pipe it to awk to deduplicate. This
is similar to piping to `sort | uniq`, except without the sorting.

package.json

@@ -72,7 +72,6 @@
     "grunt-contrib-connect": "^3.0.0",
     "grunt-contrib-copy": "^1.0.0",
     "grunt-contrib-qunit": "^5.1.1",
-    "grunt-git-authors": "^3.2.0",
     "grunt-search": "^0.1.8",
     "kleur": "4.1.5",
     "npm-reporter": "file:./test/cli/fixtures/npm-reporter",
@@ -96,7 +95,7 @@
     "test-nolint": "npm run build && npm run test-main && npm run test-cli",
     "test-integration": "npm run build && node bin/qunit.js test/integration/*.js",
     "browserstack": "browserstack-runner -v",
-    "authors": "grunt authors",
+    "authors": "(echo 'Authors ordered by first contribution\n' && git log --format='%aN <%aE>' --no-merges --reverse | awk '!seen[$0]++') | tee AUTHORS.txt",
     "coverage": "npm run build-coverage && npm run coverage-cli && npm run coverage-main && nyc report",
     "coverage-cli": "nyc --use-spawn-wrap --silent bin/qunit.js test/cli/*.js",
     "coverage-main": "nyc instrument --in-place qunit/ && grunt connect:base qunit"