fix: add missing 'use strict' directives (#780)

<!-- What / Why -->
<!-- Describe the request in detail. What it does and why it's being
changed. -->
Adds missing `'use strict'` directives; this directive is dotted around
a handful of files in the repo so this PR adds it to the rest of the CJS
files.


The local eslint file has been updated to enforce this going forward, as
suggested in the linked issue.

## References
Closes #774 
<!-- Examples:
  Related to #0
  Depends on #0
  Blocked by #0
  Fixes #0
  Closes #0
-->

Author: Fdawgs

.eslintrc.local.js

@@ -12,6 +12,7 @@ module.exports = {
           },
         ],
         'import/no-nodejs-modules': ['error'],
+        strict: ['error', 'global'],
       },
     },
   ],

benchmarks/bench-compare.js

@@ -1,3 +1,5 @@
+'use strict'
+
 const Benchmark = require('benchmark')
 const SemVer = require('../classes/semver')
 const suite = new Benchmark.Suite()

benchmarks/bench-diff.js

@@ -1,3 +1,5 @@
+'use strict'
+
 const Benchmark = require('benchmark')
 const diff = require('../functions/diff')
 const suite = new Benchmark.Suite()

benchmarks/bench-parse-options.js

@@ -1,3 +1,5 @@
+'use strict'
+
 const Benchmark = require('benchmark')
 const parseOptions = require('../internal/parse-options')
 const suite = new Benchmark.Suite()

benchmarks/bench-parse.js

@@ -1,3 +1,5 @@
+'use strict'
+
 const Benchmark = require('benchmark')
 const parse = require('../functions/parse')
 const { MAX_SAFE_INTEGER } = require('../internal/constants')

benchmarks/bench-satisfies.js

@@ -1,3 +1,5 @@
+'use strict'
+
 const Benchmark = require('benchmark')
 const satisfies = require('../functions/satisfies')
 const suite = new Benchmark.Suite()

benchmarks/bench-subset.js

@@ -1,3 +1,5 @@
+'use strict'
+
 const Benchmark = require('benchmark')
 const subset = require('../ranges/subset')
 const suite = new Benchmark.Suite()

bin/semver.js

@@ -3,6 +3,8 @@
 // Exits successfully and prints matching version(s) if
 // any supplied version is valid and passes all tests.
 
+'use strict'
+
 const argv = process.argv.slice(2)
 
 let versions = []

classes/comparator.js

@@ -1,3 +1,5 @@
+'use strict'
+
 const ANY = Symbol('SemVer ANY')
 // hoisted class for cyclic dependency
 class Comparator {

classes/index.js

@@ -1,3 +1,5 @@
+'use strict'
+
 module.exports = {
   SemVer: require('./semver.js'),
   Range: require('./range.js'),