Docs: Clarify global-require inside try/catch (fixes #3834)

docs/rules/global-require.md

@@ -6,7 +6,7 @@ In Node.js, module dependencies are included using the `require()` function, suc
 var fs = require("fs");
 ```
 
-While `require()` may be called anywhere in code, some style guide prescribe that it should be called only in the top-level scope of a module to make it easier to identify dependencies. For instance, it's arguably harder to identify dependencies when they are deeply nested inside of functions and other statements:
+While `require()` may be called anywhere in code, some style guides prescribe that it should be called only in the top level of a module to make it easier to identify dependencies. For instance, it's arguably harder to identify dependencies when they are deeply nested inside of functions and other statements:
 
 ```js
 function foo() {
@@ -19,9 +19,11 @@ function foo() {
 
 Since `require()` does a synchronous load, it can cause performance problems when used in other locations.
 
+Further, ES6 modules mandate that `import` and `export` statements can only occur in the top level of the module's body.
+
 ## Rule Details
 
-This rule requires all calls to `require()` to be at the top-level module scope.
+This rule requires all calls to `require()` to be at the top level of the module, similar to ES6 `import` and `export` statements, which also can occur only at the top level.
 
 You can enable this rule with the following syntax:
 
@@ -90,4 +92,4 @@ var x = require("x"),
 
 ## When Not To Use It
 
-If you have a module that must be initialized with information that comes from the file-system or if a module is only used in very rare situations and will cause significant overhead to load it may make sense to disable the rule.
+If you have a module that must be initialized with information that comes from the file-system or if a module is only used in very rare situations and will cause significant overhead to load it may make sense to disable the rule. If you need to `require()` an optional dependency inside of a `try`/`catch`, you can disable this rule for just that dependency using the `// eslint disable-line global-require` comment.