Fix the three review findings on README.md

Lists `env` under Settings, so the sentences that say every key names a
setting are true. Says how `--skip-errors` reports a file whose blob
cannot be read. Counts the commands that refuse a changed destination
as five, instead of pointing at the wrong list with "these".

Model: fable-5-1

README.md

@@ -625,8 +625,10 @@ Flags:
 - `--verify`: after the restore, read every restored regular file and check its
   chunk hashes.
 
-With `--skip-errors`, a file that cannot be restored is reported and skipped,
+With `--skip-errors`, a file that cannot be restored is skipped, and the command
-and the command exits non-zero. `--verify` does not check a skipped file.
+exits non-zero. Each skipped file is named, except a file that needs a blob that
+cannot be read. Such a blob is reported once, with the number of files that need
+it. `--verify` does not check a skipped file.
 
 ### `prune`
 
@@ -914,6 +916,9 @@ A command that reads the config fails when the path from `--config` or
     - Default: `index.sqlite` in the platform data directory. By default that is
       `~/.local/share/vaultik/` on Linux and
       `~/Library/Application Support/vaultik/` on macOS.
+- `env`
+    - Environment variables that `vaultik` sets in its own process when it loads
+      the config. Its keys are variable names.
 
 Sizes take a number of bytes or a unit. `MB` and `GB` are powers of 1000. `MiB`
 and `GiB` are powers of 1024. A value that is not a size is refused when the
@@ -1111,8 +1116,8 @@ there.
 A backup saves the configured destination in the local index once it has written
 the marker file there. A backup that fails earlier saves nothing, so a mistyped
 `storage_url` can be corrected. `prune`, `snapshot purge`, `snapshot remove` and
-`remote nuke` never save it. These commands refuse to run when the config names
+`remote nuke` never save it. Five commands refuse to run when the config names a
-a different destination from the saved one:
+different destination from the saved one:
 
 - `snapshot create`
 - `snapshot purge`