docs: added architecture documentation

.docs/architecture.md

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+# Architecture
+
+Juno's architecture is quite straightforward. It operates by utilizing a `HeightQueue`, which is essentially a buffered
+channel of block heights. This queue gets populated with consecutive block heights when the `start` command is
+initiated. The heights added to this queue are determined by the parameters provided to the command, such as the `start`
+and `end` height, in addition to the current chain height and the latest height stored in the database.
+
+To populate the queue, a simple `for` loop is utilized, iterating from the calculated `start` height to the
+computed `end` height. If no end height is specified, the parser will continuously enqueue new heights.
+
+Simultaneously, there are `n` workers (the number can be specified in the configuration) constantly monitoring the
+queue. These workers perform the following actions for each block height:
+
+1. Query the details of the block with the given height from the chain.
+2. Parse the transactions and messages within the block, along with other relevant details.
+3. Store the block, transactions, and messages data in a PostgreSQL database.
+4. Pass the parsed data to additional registered modules managed by the `Registrar` interface. These modules can then
+   execute additional actions tailored to specific use cases for the chain. For
+   instance, [Athena](https://github.com/desmos-labs/athena), which is a custom Juno implementation by Desmos, also
+   stores data related to Desmos profiles, relationships, and other Desmos-specific elements.
+
+![Architecture](./.img/architecture.png)