[tools] Remove prettier script and create doc formatter

Signed-off-by: Jean-Baptiste <jeanbaptiste.charron@outlook.fr>

docs/FORMATTER.md

@@ -0,0 +1,12 @@
+# C++/Java formatter
+
+We use [Clang format](https://clang.llvm.org/docs/ClangFormat.html) to format C++ and Java files.
+To format code, run `./tools/unix/clang-format.sh`
+
+# Markdown formatter
+
+We use [Prettier](https://github.com/prettier/prettier) to format Markdown and yaml files.
+To format files:
+- `npm install prettier`
+- `prettier --write README.md docs/*.md tools/python/**/*.md`
+- `prettier --write .prettierrc.yaml .forgejo/**/*.yaml .forgejo/*.yml`