docs(readme): add PowerShell, replace example

Emphasize initool never changes the input file.

README.md

@@ -53,6 +53,7 @@ The global options `-i`/`--ignore-case` and `-p`/`--pass-through` must precede t
 When given a valid command, initool first reads the INI file `filename` in its entirety.
 If the filename is `-`, initool reads standard input. For the commands `get`, `set`, `replace`, and `delete`, it then prints to standard output the file's contents with the desired change.
 For `exists`, it reports whether the section or the property exists through its exit status.
+**Initool never modifies the original file.**
 
 An INI file consists of properties (`key=value` lines) and sections (designated with a `[section name]` header line).
 A property can be at the "top level" of the file (before any section headers) or in a section (after a section header).
@@ -131,6 +132,14 @@ initool delete settings.ini test | initool set - "" cache 1024 > settings.ini.ne
 move /y settings.ini.new settings.ini
 ```
 
+You can use pipelines in PowerShell.
+The variable `$?` will be `True` only if all commands in the pipeline succeed.
+
+```powershell
+./initool delete settings.ini test | ./initool set - '' cache 1024 > settings.ini.new
+if ($?) { move -Force settings.ini.new settings.ini }
+```
+
 #### Both
 
 To retrieve only the value of a property rather than the whole property (the section, key, and value), use the flag `-v` or `--value-only`:
@@ -143,6 +152,23 @@ $ initool get tests/test.ini foo name1 --value-only
 foo1
 ```
 
+To replace text in a value, use `replace`.
+
+```sh
+$ initool get tests/replace-part.ini
+key=A longer value.
+another-key=ABAABBAAABBB
+empty=
+$ initool replace tests/replace-part.ini "" key value string
+key=A longer string.
+another-key=ABAABBAAABBB
+empty=
+> ./initool replace tests/replace-part.ini "" empty "" no
+key=A longer value.
+another-key=ABAABBAAABBB
+empty=no
+```
+
 ### Whitespace
 
 Initool defines whitespace as any mix of space and tab characters.