Add nullish coalescing to multiple articles, refactor operators, renumber the chapter

1-js/02-first-steps/14-switch/1-rewrite-switch-if-else/solution.md

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+To precisely match the functionality of `switch`, the `if` must use a strict comparison `'==='`.
+
+For given strings though, a simple `'=='` works too.
+
+```js no-beautify
+if(browser == 'Edge') {
+  alert("You've got the Edge!");
+} else if (browser == 'Chrome'
+ || browser == 'Firefox'
+ || browser == 'Safari'
+ || browser == 'Opera') {
+  alert( 'Okay we support these browsers too' );
+} else {
+  alert( 'We hope that this page looks ok!' );
+}
+```
+
+Please note: the construct `browser == 'Chrome' || browser == 'Firefox' …` is split into multiple lines for better readability.
+
+But the `switch` construct is still cleaner and more descriptive.

1-js/02-first-steps/14-switch/1-rewrite-switch-if-else/task.md

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+importance: 5
+
+---
+
+# Rewrite the "switch" into an "if"
+
+Write the code using `if..else` which would correspond to the following `switch`:
+
+```js
+switch (browser) {
+  case 'Edge':
+    alert( "You've got the Edge!" );
+    break;
+
+  case 'Chrome':
+  case 'Firefox':
+  case 'Safari':
+  case 'Opera':
+    alert( 'Okay we support these browsers too' );
+    break;
+
+  default:
+    alert( 'We hope that this page looks ok!' );
+}
+```
+