Add codespell support (CI to check, not to fix) and make it fix a few typos (#10297)

Another token of gratitude for a super useful tool and service.

More about codespell: https://github.com/codespell-project/codespell .

I personally introduced it to dozens if not hundreds of projects already
and so far only positive feedback.

CI workflow has 'permissions' set only to 'read' so also should be safe.

---------

Signed-off-by: Yaroslav O. Halchenko <debian@onerussian.com>

certbot-compatibility-test/nginx/nginx-roundtrip-testdata/chive/chive-nginx-master/reverse_proxy.conf

@@ -2,7 +2,7 @@
 
 ### Configuration for reverse proxy. Passing the necessary headers to
 ### the backend. Nginx doesn't tunnel the connection, it opens a new
-### one. Hence whe need to send these headers to the backend so that
+### one. Hence we need to send these headers to the backend so that
 ### the client(s) IP is available to them. The host is also sent.
 
 proxy_set_header X-Real-IP $remote_addr;

certbot-compatibility-test/nginx/nginx-roundtrip-testdata/chive/chive-nginx-master/win-utf

@@ -30,7 +30,7 @@ charset_map  windows-1251  utf-8 {
 
     A4  C2A4 ;   # currency sign
     A5  D290 ;   # capital Ukrainian soft G
-    A6  C2A6 ;   # borken bar
+    A6  C2A6 ;   # broken bar
     A7  C2A7 ;   # section sign
     A8  D081 ;   # capital YO
     A9  C2A9 ;   # (C)

certbot-compatibility-test/nginx/nginx-roundtrip-testdata/piwik/nginx.conf

@@ -24,7 +24,7 @@ server {
 
     # Disallow any usage of piwik assets if referer is non valid.
     location ~* ^.+\.(?:jpg|png|css|gif|jpeg|js|swf)$ {
-             # Defining the valid referers.
+             # Defining the valid referrers.
              valid_referers none blocked *.mysite.com othersite.com;
              if ($invalid_referer)  {
                 return 444;