spelling fixes [ci skip]

as detected by codespell 1.14.0

Closes https://github.com/curl/curl/pull/3114
Reviewed-by: Marcel Raad <Marcel.Raad@teamviewer.com>

docs/CONTRIBUTE.md

@@ -168,7 +168,7 @@ ways. Every pull request is verfied that:
  - ... code coverage doesn't shrink drastically
 
 If the pull-request fails one of these tests, it will show up as a red X and
-you are expected to fix the problem. If you don't understand whan the issue is
+you are expected to fix the problem. If you don't understand when the issue is
 or have other problems to fix the complaint, just ask and other project
 members will likely be able to help out.
 

docs/FAQ

@@ -874,7 +874,7 @@ FAQ
 
     4.5.3 "403 Forbidden"
 
-    The server understood the request, but is refusing to fulfil it.
+    The server understood the request, but is refusing to fulfill it.
     Authorization will not help and the request SHOULD NOT be repeated.
 
     4.5.4 "404 Not Found"

docs/TODO

@@ -788,7 +788,7 @@ that doesn't exist on the server, just like --ftp-create-dirs.
 
  AIA can provide various things like CRLs but more importantly information
  about intermediate CA certificates that can allow validation path to be
- fullfilled when the HTTPS server doesn't itself provide them.
+ fulfilled when the HTTPS server doesn't itself provide them.
 
  Since AIA is about downloading certs on demand to complete a TLS handshake,
  it is probably a bit tricky to get done right.

docs/libcurl/curl_url_get.3

@@ -57,7 +57,7 @@ default port for the scheme.
 Asks \fIcurl_url_get(3)\fP to URL decode the contents before returning it. It
 will not attempt to decode the scheme, the port number or the full URL.
 
-The query component will also get plus-to-space convertion as a bonus when
+The query component will also get plus-to-space conversion as a bonus when
 this bit is set.
 
 Note that this URL decoding is charset unaware and you will get a zero

docs/libcurl/curl_url_set.3

@@ -105,7 +105,7 @@ If set, will make libcurl allow the URL to be set without a scheme and it
 instead "guesses" which scheme that was intended based on the host name.  If
 the outermost sub-domain name matches DICT, FTP, IMAP, LDAP, POP3 or SMTP then
 that scheme will be used, otherwise it picks HTTP. Conflicts with the
-\fICURLU_DEFAULT_SCHEME\fP option which takes precendence if both are set.
+\fICURLU_DEFAULT_SCHEME\fP option which takes precedence if both are set.
 .SH RETURN VALUE
 Returns a CURLUcode error value, which is CURLUE_OK (0) if everything went
 fine.