This PR improves the logging module a tad bit along with the
documentation.
**New Look:**
## Usage
**General Logger**
InvokeAI has a module level logger. You can call it this way.
In this below example, you will use the default logger `InvokeAI` and
all your messages will be logged under that name.
```python
from invokeai.backend.util.logging import logger
logger.critical("CriticalMessage") // In Bold Red
logger.error("Info Message") // In Red
logger.warning("Info Message") // In Yellow
logger.info("Info Message") // In Grey
logger.debug("Debug Message") // In Grey
```
Results:
```
[12-05-2023 20]::[InvokeAI]::CRITICAL --> This is an info message [In Bold Red]
[12-05-2023 20]::[InvokeAI]::ERROR --> This is an info message [In Red]
[12-05-2023 20]::[InvokeAI]::WARNING --> This is an info message [In Yellow]
[12-05-2023 20]::[InvokeAI]::INFO --> This is an info message [In Grey]
[12-05-2023 20]::[InvokeAI]::DEBUG --> This is an info message [In Grey]
```
**Custom Logger**
If you want to use a custom logger for your module, you can import it
the following way.
```python
from invokeai.backend.util.logging import logging
logger = logging.getLogger(name='Model Manager')
logger.critical("CriticalMessage") // In Bold Red
logger.error("Info Message") // In Red
logger.warning("Info Message") // In Yellow
logger.info("Info Message") // In Grey
logger.debug("Debug Message") // In Grey
```
Results:
```
[12-05-2023 20]::[Model Manager]::CRITICAL --> This is an info message [In Bold Red]
[12-05-2023 20]::[Model Manager]::ERROR --> This is an info message [In Red]
[12-05-2023 20]::[Model Manager]::WARNING --> This is an info message [In Yellow]
[12-05-2023 20]::[Model Manager]::INFO --> This is an info message [In Grey]
[12-05-2023 20]::[Model Manager]::DEBUG --> This is an info message [In Grey]
```
**When to use custom logger?**
It is recommended to use a custom logger if your module is not a part of
base InvokeAI. For example: custom extensions / nodes.
