feat(styles.css): create variables for colours used across website

styles.css

+/* Globals */
+
+:root {
+    /** This is the primary background colour for the website **/
+        /* USAGE: index.html:hero && rules.html:rules && All borders */
+            --main-dark: #03080c;
+
+    /** These are colours used for the main sections of the website **/
+
+        /* USAGE: index.html:about && location.html:directions */
+            --section-blue: #194263;
+
+        /* USAGE: index.html:sign-up-form && location.html:map */
+            --section-pink: #fb5aba;
+
+        /* USAGE: rules.html:rules */ 
+            --section-baby-pink: #fd98d4;
+
+        /* USAGE: about.html:hero */
+            --section-purple: #6e539a;
+
+        /* USAGE: about.html:about */
+            --section-purple-saturated: #6f277b;
+
+    /** The colour of checked items in the sign up form **/
+        /* USAGE: index.html:sign-up-form > online-in-person && index.html:sign-up-form > interests */
+            --form-filled: #2c74ae;
+
+    /** Pink accent colours used across website **/
+        /* USAGE: index.html:hero > sign up button && rules.html:rules > sign up button */
+            --accent-pink: #c30576;
+
+        /* USAGE: index.html:hero > sign up button:active && rules.html:rules > sign up button:active */
+            --accent-pink-lighter: #fa2aa6;
+        
+        /* USAGE: index.html:about > hyperlinks && locations.html:directions > hyperlinks */
+            --accent-baby-pink: #fd98d4;
+
+    /** Blue accent colours used across website **/
+        /* USAGE: 
+                index.html:sign-up-form > sign up button 
+                && about.html:hero > hyperlinks 
+                && about.html:about > hyperlinks 
+                && rules.html:rules > hyperlinks 
+                && location.html:directions > selected tab + sign up button
+        */
+            --accent-blue: #00eded;
+
+        /* USAGE: index.html:sign-up-form > sign up button:active && location.html:directions > sign up button:active */
+            --accent-blue-lighter: #54ffff;
+        
+        /* USAGE: All visited hyperlinks */
+            --accent-baby-blue: #c1ffff;
+
+        /* USAGE: Footer Background Colour */
+            --footer-purple: #1f172c;
+}