Update headers of JavaScript roadmap (#2534)

* update 103-iifes.md

Add header to free content; add new resources

* Update readme.md

add resources header

* Update 100-default-params.md

add resources header

* Update 101-rest-params.md

add resources header; correct badge title

* Update 102-arrow-functions.md

add resources header; better description for resource link, show its from MDN

* Update readme.md

add resources header; add video resource

content/roadmaps/106-javascript/content/109-javascript-functions/101-function-parameters/100-default-params.md

@@ -2,4 +2,5 @@
 
 Default function parameters allow named parameters to be initialized with default values if no value or `undefined` is passed.
 
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
 <BadgeLink colorScheme='yellow' badgeText='Read' href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Default_parameters'>Default Parameters - MDN Docs</BadgeLink>

content/roadmaps/106-javascript/content/109-javascript-functions/101-function-parameters/101-rest-params.md

@@ -2,4 +2,5 @@
 
 The rest parameter syntax allows a function to accept an indefinite number of arguments as an array, providing a way to represent [variadic functions](https://en.wikipedia.org/wiki/Variadic_function) in JavaScript.
 
-<BadgeLink colorScheme='yellow' badgeText='Rest parameters MDN documentation' href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/rest_parameters'>Rest Parameters - MDN Docs</BadgeLink>
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/rest_parameters'>Rest Parameters - MDN Docs</BadgeLink>

content/roadmaps/106-javascript/content/109-javascript-functions/101-function-parameters/readme.md

@@ -2,4 +2,5 @@
 
 The parameter is the name given to the variable declared inside the definition of a function. There are two special kinds of syntax: default and rest parameters.
 
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
 <BadgeLink colorScheme="yellow" badgeText="Read" href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Functions#function_parameters">Function Parameters</BadgeLink>

content/roadmaps/106-javascript/content/109-javascript-functions/102-arrow-functions.md

@@ -2,5 +2,6 @@
 
 Arrow Function is a new way of creating functions with the '=>' operator with a shorter syntax.
 
-<BadgeLink colorScheme="yellow" badgeText="Read" href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions">Arrow function expressions</BadgeLink>
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+<BadgeLink colorScheme="yellow" badgeText="Read" href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions">MDN - Arrow Function Expressions</BadgeLink>
 <BadgeLink colorScheme="yellow" badgeText="Read" href="https://www.w3schools.com/js/js_arrow_function.asp">JavaScript Arrow Function</BadgeLink>

content/roadmaps/106-javascript/content/109-javascript-functions/103-iifes.md

@@ -2,4 +2,6 @@
 
 Immediately-Invoked Function Expression is a function that is executed immediately after it is created.
 
-<BadgeLink colorScheme="yellow" badgeText="Read" href="https://developer.mozilla.org/en-US/docs/Glossary/IIFE">IIFE — MDN Docs</BadgeLink>
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+<BadgeLink colorScheme="yellow" badgeText="Read" href="https://developer.mozilla.org/en-US/docs/Glossary/IIFE">IIFE — MDN Docs</BadgeLink>
+<BadgeLink colorScheme="yellow" badgeText="Read" href="https://javascript.plainenglish.io/https-medium-com-javascript-in-plain-english-stop-feeling-iffy-about-using-an-iife-7b0292aba174">JavaScript in Plain English - IIFE</BadgeLink>

content/roadmaps/106-javascript/content/109-javascript-functions/readme.md

@@ -2,4 +2,6 @@
 
 Functions are blocks of code that execute whenever they are invoked. They are useful for placing code snippets executed in different places in the code.
 
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
 <BadgeLink colorScheme="yellow" badgeText="Read" href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Functions">Functions - MDN Docs</BadgeLink>
+<BadgeLink badgeText='Watch' href='https://youtu.be/N8ap4k_1QEQ'>JavaScript Functions - Programming with Mosh</BadgeLink>