docs(discord-caching): add doxygen group

Add doxygen group, make comments consistent to other headers

include/discord-cache.h

@@ -1,6 +1,17 @@
+/**
+ * @file discord-cache.h
+ * @author Cogmasters
+ * @brief Caching of Discord resources
+ */
+
 #ifndef DISCORD_CACHE_H
 #define DISCORD_CACHE_H
 
+/** @defgroup DiscordClientCache Caching
+ * @ingroup DiscordClient
+ * @brief Caching API supported by Concord
+ *  @{ */
+
 enum discord_cache_options {
     DISCORD_CACHE_MESSAGES = 1 << 0,
     DISCORD_CACHE_GUILDS = 1 << 1,
@@ -10,26 +21,31 @@ void discord_cache_enable(struct discord *client,
                           enum discord_cache_options options);
 
 /**
- * @brief get a message from cache, only if locally available in RAM
- * @note you must call discord_unclaim(client, message) when done
- * 
+ * @brief Get a message from cache, only if locally available in RAM
+ * @note When done, discord_unclaim() must be called on the message resource
+ *
  * @param client the client initialized with discord_init()
  * @param channel_id the channel id the message is in
  * @param message_id the id of the message
- * @return NULL if not found, or the message from the cache
+ * @return `NULL` if not found, or a cache'd message
  */
 const struct discord_message *discord_cache_get_channel_message(
     struct discord *client, u64snowflake channel_id, u64snowflake message_id);
 
 /**
- * @brief get a guild from cache, only if locally available in RAM
- * @note you must call discord_unclaim(client, guild) when done
- * 
+ * @brief Get a guild from cache, only if locally available in RAM
+ * @note When done, discord_unclaim() must be called on the guild resource
+ *
  * @param client the client initialized with discord_init()
  * @param guild_id the id of the guild
- * @return NULL if not found, or the guild from the cache
+ * @return `NULL` if not found, or a cache'd guild
  */
-const struct discord_guild *discord_cache_get_guild(
-    struct discord *client, u64snowflake guild_id);
+const struct discord_guild *discord_cache_get_guild(struct discord *client,
+                                                    u64snowflake guild_id);
+
+/** @example cache.c
+ * Demonstrates cache usage */
+
+/** @} DiscordClientCache */
 
-#endif // !DISCORD_CACHE_H
+#endif /* DISCORD_CACHE_H */