Initial contribution (#14529)

Signed-off-by: Jacob Laursen <jacob-github@vindvejr.dk>

bundles/org.openhab.transform.vat/README.md

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+# VAT Transformation Service
+
+The VAT Transformation Service adds VAT (Value-Added Tax) to a given input amount.
+The input string must be either an ISO 3166 alpha-2 country code or a percentage, i.e. numerical format.
+
+## Examples
+
+### Display
+
+```java
+Number CurrentSpotPrice "Current Spot Price incl. VAT [VAT(12.5):%s]" <price>
+```
+
+### In a Rule
+
+Add Danish VAT to price:
+
+```java
+var Number price = 499
+logInfo("Price", "Price incl. VAT: " + transform("VAT", "DK", price.toString))
+```
+
+## Usage as a Profile
+
+The functionality of this `TransformationService` can also be used in a `Profile` on an `ItemChannelLink`.
+This is the most powerful usage since VAT will be added without providing any explicit country code, percentage or configuration.
+To use this, an `.items` file can be configured as follows:
+
+```java
+Number CurrentSpotPrice "Current Spot Price" <price> { channel="<channelUID>" [profile="transform:VAT"] }
+```
+
+To override VAT percentage for configured system country:
+
+```java
+Number CurrentSpotPrice "Current Spot Price" <price> { channel="<channelUID>" [profile="transform:VAT", percentage="12.5"] }
+```
+
+If VAT is not known for the configured country or the provided percentage is invalid, the default is 0%, so the input value will be put into the transformation without any changes.
+
+Please note: This profile is a one-way transformation, i.e. only values from a device towards the item are changed, the other direction is left untouched.