docs(bump): Document the use of tag_format variables with curly brackets

Author: grahamhar

docs/bump.md

@@ -433,18 +433,24 @@ In your `pyproject.toml` or `.cz.toml`
 tag_format = "v$major.$minor.$patch$prerelease"
 ```
 
-The variables must be preceded by a `$` sign. Default is `$version`.
+The variables must be preceded by a `$` sign and optionally can be wrapped in `{}` . Default is `$version`.
 
 Supported variables:
 
-| Variable      | Description                                 |
-| ------------- | ------------------------------------------- |
-| `$version`    | full generated version                      |
-| `$major`      | MAJOR increment                             |
-| `$minor`      | MINOR increment                             |
-| `$patch`      | PATCH increment                             |
-| `$prerelease` | Prerelease (alpha, beta, release candidate) |
-| `$devrelease` | Development release                         |
+| Variable        | Description                                 |
+|-----------------|---------------------------------------------|
+| `$version`      | full generated version                      |
+| `$major`        | MAJOR increment                             |
+| `$minor`        | MINOR increment                             |
+| `$patch`        | PATCH increment                             |
+| `$prerelease`   | Prerelease (alpha, beta, release candidate) |
+| `$devrelease`   | Development release                         |
+| `${version}`    | full generated version                      |
+| `${major}`      | MAJOR increment                             |
+| `${minor}`      | MINOR increment                             |
+| `${patch}`      | PATCH increment                             |
+| `${prerelease}` | Prerelease (alpha, beta, release candidate) |
+| `${devrelease}` | Development release                         |
 
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