feat(docs): ADR on the consensus Write-Ahead Log (WAL) (#1408)

Closes #469.


[Rendered](https://github.com/cason/malachite/blob/adr-wal/docs/architecture/adr-007-write-ahead-log.md)

---------

Co-authored-by: Anca Zamfir <ancazamfir@users.noreply.github.com>
Co-authored-by: nenadmilosevic95 <nenad.milosevic@circle.com>

Author: 3 people

docs/architecture/readme.md docs/architecture/README.mddocs/architecture/readme.md renamed to docs/architecture/README.md

@@ -25,11 +25,12 @@ To suggest an ADR, please make use of the [ADR template](./adr-template.md) prov
 
 ## Table of Contents
 
-| ADR \#                                      | Description                                 | Status                |
-|---------------------------------------------|---------------------------------------------|-----------------------|
-| [001](./adr-001-architecture.md)            | High Level Architecture                     | Accepted              |
-| [002](./adr-002-node-actor.md)              | Node Architecture using the Actor Model     | Accepted              |
-| [003](./adr-003-values-propagation.md)      | Propagation of Proposed Values              | Accepted              |
-| [004](./adr-004-coroutine-effect-system.md) | Coroutine-Based Effect System for Consensus | Accepted              |
-| [005](./adr-005-value-sync.md)              | Value Sync Protocol                         | Accepted              |
-| [006](./adr-006-proof-of-validator.md)      | Proof-of-Validator Protocol                 | Accepted              |
+| ADR \#                                      | Description                                 | Status   |
+|---------------------------------------------|---------------------------------------------|----------|
+| [001](./adr-001-architecture.md)            | High Level Architecture                     | Accepted |
+| [002](./adr-002-node-actor.md)              | Node Architecture using the Actor Model     | Accepted |
+| [003](./adr-003-values-propagation.md)      | Propagation of Proposed Values              | Accepted |
+| [004](./adr-004-coroutine-effect-system.md) | Coroutine-Based Effect System for Consensus | Accepted |
+| [005](./adr-005-value-sync.md)              | Value Sync Protocol                         | Accepted |
+| [006](./adr-006-proof-of-validator.md)      | Proof-of-Validator Protocol                 | Accepted |
+| [007](./adr-007-write-ahead-log.md)         | Consensus Write-Ahead Log (WAL)             | Accepted |