docs: add more notes

docs/changelog.md

@@ -2,6 +2,8 @@
 
 Critical security updates are indicated by the :warning: icon.
 
+This changelog is not an exhaustive list. Code refactorings, minor bug fixes, documentation/dependency updates, etc. are usually not listed here. If you want to see all changes, click on the version number and check the commit history.
+
 - Server administrators must check [notice-for-admins.md](https://firefish.dev/firefish/firefish/-/blob/main/docs/notice-for-admins.md) as well.
 - Third-party client/bot developers may want to check [api-change.md](https://firefish.dev/firefish/firefish/-/blob/main/docs/api-change.md) as well.
 

docs/install.md

@@ -1,8 +1,12 @@
 # Install Firefish
 
+Please check the [v20240206 release note](https://firefish.dev/firefish/firefish/-/releases/v20240206) first. This project is barely maintained for those who really want to keep using Firefish. Please understand this before proceeding.
+
+## Dependencies
+
 Firefish depends on the following software.
 
-## Runtime dependencies
+### Runtime dependencies
 
 - At least [NodeJS](https://nodejs.org/en/) v18.19.0 (v20/v22 recommended)
 - At least [PostgreSQL](https://www.postgresql.org/) v12 (v16 recommended) with [PGroonga](https://pgroonga.github.io/) extension
@@ -17,7 +21,7 @@ Firefish depends on the following software.
   - [KeyDB](https://keydb.dev/)
   - Another [Redis](https://redis.io/) / [Valkey](https://valkey.io/) server
 
-## Build dependencies
+### Build dependencies
 
 - At least [Rust](https://www.rust-lang.org/) v1.74
 - C/C++ compiler & build tools (like [GNU Make](https://www.gnu.org/software/make/))