docs(config options): rewrite allowedVersions (#29014)

docs/usage/configuration-options.md

@@ -2473,8 +2473,9 @@ For example you have multiple `package.json` and want to use `dependencyDashboar
 
 ### allowedVersions
 
-Use this - usually within a packageRule - to limit how far to upgrade a dependency.
-For example, if you wish to upgrade to Angular v1.5 but not to `angular` v1.6 or higher, you could define this to be `<= 1.5` or `< 1.6.0`:
+You can use `allowedVersions` - usually within a `packageRules` entry - to limit how far to upgrade a dependency.
+
+For example, if you want to upgrade to Angular v1.5 but _not_ to `angular` v1.6 or higher, you could set `allowedVersions` to `<= 1.5` or `< 1.6.0`:
 
 ```json
 {
@@ -2487,10 +2488,14 @@ For example, if you wish to upgrade to Angular v1.5 but not to `angular` v1.6 or
 }
 ```
 
-The valid syntax for this will be calculated at runtime because it depends on the versioning scheme, which is itself dynamic.
+Renovate calculates the valid syntax for this at runtime, because it depends on the dynamic versioning scheme.
+
+#### Using regular expressions
+
+You can use Regular Expressions in the `allowedVersion` config.
+You must _begin_ and _end_ your Regular Expression with the `/` character!
 
-This field also supports Regular Expressions if they begin and end with `/`.
-For example, the following will enforce that only 3 or 4-part versions are supported, without any prefixes:
+For example, this config only allows 3 or 4-part versions, without any prefixes in the version:
 
 ```json
 {
@@ -2503,8 +2508,12 @@ For example, the following will enforce that only 3 or 4-part versions are suppo
 }
 ```
 
-This field also supports a special negated regex syntax for ignoring certain versions.
-Use the syntax `!/ /` like the following:
+Again: note how the Regular Expression _begins_ and _ends_ with the `/` character.
+
+#### Ignore versions with negated regex syntax
+
+You can use a special negated regex syntax to ignore certain versions.
+You must use the `!/ /` syntax, like this:
 
 ```json
 {