Run codespell on the entire codebase

This tool detects and fixes common English spelling mistakes, with
generally very few mistakes.

Here is the command I used to generate this commit.  There were a few
changes that had to be done manually, and of course adding the ignore
file:
```shell
codespell -I .codespell-ignore -x .codespell-ignore -w
```

I didn’t add it to the CI, but this would be a good place for it.

pipewire-pulseaudio/src/json.c

@@ -197,7 +197,7 @@ static const char* parse_string(const char *str, pa_json_object *obj) {
                     goto error;
 
                 default:
-                    pa_log("Unexepcted escape value: %c", *str);
+                    pa_log("Unexpected escape value: %c", *str);
                     goto error;
             }
         }