prism-converter: Add README

src/prism-converter/README.md

+# Prism converter
+
+This directory containers a helper program called `prism-converter` that
+converts transition matrices of PRISM[1] models into coalgebra specifications.
+
+## Building
+
+```sh
+stack build --flag copar:benchmark-generators
+```
+
+## Generating transition matrices
+
+You can generate those transition matrices with PRISM itself by using:
+
+```sh
+prism -exporttrans TRA_FILE -exportstates STA_FILE -const CONST_ASSIGNMENTS
+```
+
+Given the constant assignments `CONST_ASSIGNMENTS` (see the PRISM documentation
+on syntax and semantics of those), thsi output a transition matrix in `TRA_FILE`
+and a states file in `STA_FILE`. Please see [2] for additional details.
+
+## Converting them into coalgebra specs
+
+The resulting files can then be converted into a coalgebra specification using
+
+```sh
+stack exec prism-converter -- --model-type TYPE --states-file STA_FILE TRA_FILE
+```
+
+where type is one of dtmc, ctmc or mdp.
+
+See `stack exec prism-converter -- --help` for details.
+
+[1]: https://www.prismmodelchecker.org
+[2]: https://www.prismmodelchecker.org/manual/RunningPRISM/ExportingTheModel