Pimp the docs linter (and assorted changes) (#2553)

### Pimp the docs linter (and assorted changes)

 #### `scripts/lint-docs.js`

- Add an optional cache for faster runs
- Add a final report
- Don't return anything from `exec()`
- Cover more files

 #### `scripts/_command.js`

- Look for a "--cache" option

 #### `package.json` scripts

- Added `watch:lint-docs`
- Added `cleanup:lint` to remove the eslint and lint-docs cache files
- Changed `lint:docs` to use the `--cache` option
- Added `test:js` so that we can run the test suite without the linter
- Changed `test` to defer to `test:js`

 #### Actual lint fixes:

- Bad link in a migration guide
- The unicode dashes in the "https://en.wikipedia.org/wiki/Subject–verb–object" are not escaped by marked

### Some more lint-docs pimping

#### `scripts/lint-docs.js`

- some code reorg and cleanup (take a hint from the local coding conventions)
- fix misc bugs
- pass a User-Agent header to the requests
- even nicer reporting

#### `package.json`

- bump the @babel/parser dep to the latest

#### Docs

- tweaks based on lints missed due to previous bugs

### Docs: use the github page for velocity.js, the home page has too many errors.

Co-Authored-By: Isiah Meadows <contact@isiahmeadows.com>

package.json

@@ -11,25 +11,27 @@
     "watch": "run-p watch:**",
     "watch:js": "node scripts/bundler browser.js -output mithril.js -watch",
     "watch:docs": "node scripts/generate-docs --watch",
+    "watch:docs-lint": "node scripts/lint-docs --watch",
     "build": "run-p build:browser build:min build:stream-min",
     "build:browser": "node scripts/bundler browser.js -output mithril.js",
     "build:docs": "node scripts/generate-docs",
     "build:min": "node scripts/bundler browser.js -output mithril.min.js -minify -save",
     "build:stream-min": "node scripts/minify-stream",
+    "cleanup:lint": "rimraf .eslintcache .lint-docs-cache",
     "lint": "run-s -cn lint:**",
     "lint:js": "eslint . --cache",
-    "lint:docs": "node scripts/lint-docs",
+    "lint:docs": "node scripts/lint-docs --cache",
     "perf": "node performance/test-perf.js",
     "pretest": "npm run lint",
-    "test": "node ospec/bin/ospec",
-    "posttest": "npm run lint",
+    "test": "run-s test:js",
+    "test:js": "node ospec/bin/ospec",
     "cover": "istanbul cover --print both ospec/bin/ospec",
     "release": "npm version -m 'v%s'",
     "version": "npm run build && git add mithril.js mithril.min.js stream.js stream.min.js README.md"
   },
   "devDependencies": {
     "@alrra/travis-scripts": "^3.0.1",
-    "@babel/parser": "^7.6.2",
+    "@babel/parser": "^7.7.5",
     "benchmark": "^2.1.4",
     "chokidar": "^3.2.1",
     "escape-string-regexp": "^2.0.0",