Docs: Add configuration comments in examples

docs/rules/no-unmodified-loop-condition.md

@@ -29,6 +29,10 @@ If a reference is inside of a dynamic expression (e.g. `CallExpression`,
 Examples of **incorrect** code for this rule:
 
 ```js
+/*eslint no-unmodified-loop-condition: "error"*/
+
+var node = something;
+
 while (node) {
     doSomething(node);
 }
@@ -46,6 +50,8 @@ while (node !== root) {
 Examples of **correct** code for this rule:
 
 ```js
+/*eslint no-unmodified-loop-condition: "error"*/
+
 while (node) {
     doSomething(node);
     node = node.parent;

docs/rules/prefer-object-spread.md

@@ -9,6 +9,7 @@ Introduced in ES2018, object spread is a declarative alternative which may perfo
 Examples of **incorrect** code for this rule:
 
 ```js
+/*eslint prefer-object-spread: "error"*/
 
 Object.assign({}, foo)
 
@@ -31,6 +32,7 @@ Object.assign({ foo: bar });
 Examples of **correct** code for this rule:
 
 ```js
+/*eslint prefer-object-spread: "error"*/
 
 Object.assign(...foo);
 

docs/rules/valid-typeof.md

@@ -37,6 +37,8 @@ typeof bar === typeof qux
 Examples of **incorrect** code with the `{ "requireStringLiterals": true }` option:
 
 ```js
+/*eslint valid-typeof: ["error", { "requireStringLiterals": true }]*/
+
 typeof foo === undefined
 typeof bar == Object
 typeof baz === "strnig"
@@ -48,6 +50,8 @@ typeof foo == 5
 Examples of **correct** code with the `{ "requireStringLiterals": true }` option:
 
 ```js
+/*eslint valid-typeof: ["error", { "requireStringLiterals": true }]*/
+
 typeof foo === "undefined"
 typeof bar == "object"
 typeof baz === "string"