Revert "Add Decodal formatter"

This reverts commit 22f6bc1ab9.

doc/manual/souce/index.md

@@ -7,8 +7,7 @@ Decodal は Deferred Constraint Data Language、略称 DCDL のプロジェク
 
 1. [Introduction](./introduction.md)
 2. [Components](./components.md)
-3. [Formatting](./formatting.md)
-4. [Language Specification](./language/index.md)
+3. [Language Specification](./language/index.md)
    1. [Lexical Structure and Syntax](./language/syntax.md)
    2. [Value](./language/value/index.md)
       1. [String](./language/value/string.md)
@@ -37,7 +36,7 @@ Decodal は Deferred Constraint Data Language、略称 DCDL のプロジェク
    9. [Materialization and Errors](./language/materialization-and-errors.md)
    10. [Naming Conventions](./language/naming.md)
    11. [Examples](./language/examples.md)
-5. [Implementation Design](./design/index.md)
+4. [Implementation Design](./design/index.md)
    1. [Execution Pipeline](./design/execution-pipeline.md)
    2. [Runtime Model](./design/runtime-model.md)
    3. [Thunk and Lazy Evaluation](./design/thunk-and-lazy-evaluation.md)
@@ -45,5 +44,5 @@ Decodal は Deferred Constraint Data Language、略称 DCDL のプロジェク
    5. [Diagnostics and Fallback](./design/diagnostics-and-fallback.md)
    6. [Embedding API](./design/embedding-api.md)
    7. [Features](./design/features.md)
-6. [Development](./development.md)
-7. [Open Issues](./open-issues.md)
+5. [Development](./development.md)
+6. [Open Issues](./open-issues.md)