helpers/sharing.md: sync share options with CURLSHOPT_SHARE

- Add CURL_LOCK_DATA_PSL and CURL_LOCK_DATA_HSTS.

- Explain that some option values are not supported multi-threaded:
  CURL_LOCK_DATA_COOKIE, CURL_LOCK_DATA_CONNECT, CURL_LOCK_DATA_HSTS.

Bug: curl/curl#17774
Reported-by: [email protected]

Closes #551

Author: jay

helpers/sharing.md

@@ -40,7 +40,8 @@ the same share object.
 
 `CURL_LOCK_DATA_COOKIE` - set this bit to share cookie jar. Note that each
 easy handle still needs to get its cookie "engine" started properly to start
-using cookies.
+using cookies. It is not supported to use this option with multiple concurrent
+threads.
 
 `CURL_LOCK_DATA_DNS` - the DNS cache is where libcurl stores addresses for
 resolved hostnames for a while to make subsequent lookups faster.
@@ -52,7 +53,18 @@ connection faster.
 `CURL_LOCK_DATA_CONNECT` - when set, this handle uses a shared connection
 cache and thus is more likely to find existing connections to re-use etc,
 which may result in faster performance when doing multiple transfers to the
-same host in a serial manner.
+same host in a serial manner. It is not supported to use this option with
+multiple concurrent threads.
+
+`CURL_LOCK_DATA_PSL` - this bit shares the Public Suffix List between handles.
+The list of public suffixes, aka top-level Internet domains, is used to help
+manage the security of cookies. Sharing the list prevents overhead from having
+to process multiple copies of the list.
+
+`CURL_LOCK_DATA_HSTS` - this bit shares the in-memory HSTS (HTTP Strict
+Transport Security) cache. HSTS is used by websites to indicate that HTTP
+requests should instead be accessed securely using HTTPS. It is not supported
+to use this option with multiple concurrent threads.
 
 ## Locking