Update mg_get_http_var.md

docs/c-api/http.h/mg_get_http_var.md

@@ -7,10 +7,10 @@ signature: |
                       size_t dst_len);
 ---
 
-Fetch an HTTP form variable.
+Fetches a HTTP form variable.
 
-Fetch a variable `name` from a `buf` into a buffer specified by
-`dst`, `dst_len`. Destination is always zero-terminated. Return length
+Fetches a variable `name` from a `buf` into a buffer specified by
+`dst`, `dst_len`. The destination is always zero-terminated. Returns the length
 of a fetched variable. If not found, 0 is returned. `buf` must be
 valid url-encoded buffer. If destination is too small, `-1` is returned.