docs: new cache example and file name fixes (#862)

docpages/example_code/using_cache.cpp

@@ -0,0 +1,26 @@
+#include <dpp/dpp.h>
+
+int main() {
+    /* Create bot */
+    dpp::cluster bot("token", dpp::i_default_intents | dpp::i_guild_members);
+
+    bot.on_log(dpp::utility::cout_logger());
+
+    /* This event is fired when someone removes their reaction from a message*/
+    bot.on_message_reaction_remove([&bot](const dpp::message_reaction_remove_t& event) {
+
+        /* Find the user in the cache using his discord id */
+        dpp::user* reacting_user = dpp::find_user(event.reacting_user_id);
+
+        /* If user not found in cache, log and return */
+        if (!reacting_user) {
+            bot.log(dpp::ll_info, "User with the id " + std::to_string(event.reacting_user_id) + " was not found.");
+            return;
+        }
+
+        bot.log(dpp::ll_info, reacting_user->format_username() + " removed his reaction.");
+    });
+
+    bot.start(dpp::st_wait);
+    return 0;
+}

docpages/example_programs/the_basics.md

@@ -7,4 +7,5 @@ These example programs are great to get started with simple things in the D++ li
 * \subpage attach-file "Attaching a file"
 * \subpage webhooks "Webhooks"
 * \subpage callback-functions "Using Callback Functions"
-* \subpage editing-channels-and-messages
+* \subpage editing-channels-and-messages
+* \subpage using-cache

docpages/example_programs/the_basics/using_cache.md

@@ -0,0 +1,18 @@
+\page using-cache Using Cache
+
+Sometimes you may need information that is not directly available in the event callback object.
+
+To handle this DPP maintains a cache of commonly used data for you.
+
+@note As of August 30th, 2022, Discord made Guild Members a privileged intent. You must have GUILD_MEMBERS intent enabled for your app from discord developers portal to be able to look for members in cache.
+
+Below is an example showing how to get a user from the cache
+
+\include{cpp} using_cache.cpp 
+
+DPP caches more than just users, which you can get using the below-mentioned functions:
+- `dpp::find_role()`
+- `dpp::find_channel()`
+- `dpp::find_emoji()`
+- `dpp::find_guild()`
+- `dpp::find_guild_member()`