docs: some nitpicks

- replaced double spaces with single space where applicable
- replaced "favourite" with "favorite"
- added language identifiers to code blocks in markdown files
- added extra line after code blocks and after headings in markdown
  files

Cloes #20748

docs/libcurl/opts/CURLOPT_IOCTLFUNCTION.md

@@ -28,7 +28,7 @@ typedef enum {
   CURLIOE_LAST           /* never use */
 } curlioerr;
 
-typedef enum  {
+typedef enum {
   CURLIOCMD_NOP,         /* no operation */
   CURLIOCMD_RESTARTREAD, /* restart the read stream from start */
   CURLIOCMD_LAST         /* never use */

docs/libcurl/opts/CURLOPT_OPENSOCKETFUNCTION.md

@@ -22,7 +22,7 @@ CURLOPT_OPENSOCKETFUNCTION - callback for opening socket
 ~~~c
 #include <curl/curl.h>
 
-typedef enum  {
+typedef enum {
   CURLSOCKTYPE_IPCXN,  /* socket created for a specific IP connection */
 } curlsocktype;
 

docs/libcurl/opts/CURLOPT_SOCKOPTFUNCTION.md

@@ -22,7 +22,7 @@ CURLOPT_SOCKOPTFUNCTION - callback for setting socket options
 ~~~c
 #include <curl/curl.h>
 
-typedef enum  {
+typedef enum {
   CURLSOCKTYPE_IPCXN,  /* socket created for a specific IP connection */
   CURLSOCKTYPE_ACCEPT, /* socket created by accept() call */
   CURLSOCKTYPE_LAST    /* never use */