Update documentation and enhance system design resources

- Added new 'practice.md' file for system design interview questions with solutions, improving accessibility for candidates.
- Created 'reminder.md' to serve as a quick reference for system design solutions, guiding users through the problem-solving process.
- Updated 'design-glance.md' to clarify the design of the personal budget tracking app (Mint.com) and improved the structure of related content.
- Revised '.gitignore' to include 'site/' for mkdocs deployment and ensure proper file management.
- Made minor updates to 'mkdocs.yml' for better organization and clarity in documentation navigation.

docs/solutions/system_design/query_cache/README.md

@@ -16,10 +16,19 @@ Remember your goal is to understand the problem and establish the design scope.
 
 Here is an example of the dialog you could have with the **Interviewer**:
 **Interviewer**: Design a key-value cache to save the results of the most recent web server queries.
+
 **Candidate**: ok, do you mean deploy Redis as docker or building Redis like?
+
 **Interviewer**: I mean building Redis like.
-**Candidate**: ok, can you please explain the traffic assumptions? 
+
+**Candidate**: To clarify and understand the scope, may I start with a few quick questions?
+
+**Interviewer**: Yes, please.
+
+**Candidate**: What are the **main features, users, and use cases** of the system?
+
 **Interviewer**: Yes, the cache should be able to handle 10 million users, 10 billion queries per month.
+
 **Candidate**: ok. So here is the scope of the problem:
 
 ### Use cases
@@ -73,7 +82,7 @@ Handy conversion guide:
 
 <!-- Old image for reference ![Imgur](http://i.imgur.com/KqZ3dSx.png) -->
 
-![Imgur](http://i.imgur.com/KqZ3dSx.png) 
+![Imgur](../../../images/KqZ3dSx.png) 
 
 
 ```mermaid