chore(CONTRIBUTING.md): enforce commit guidelines

CONTRIBUTING.md

@@ -296,6 +296,51 @@ OS and is built by Android NDK. This often introduces compatibility issues as
 Android (specifically Termux) is not a standard platform. Do not expect there
 are exist package recipes available out-of-box.
 
+## Commit guidelines
+
+A commit message should look something like:
+```
+<commitType>(<repo>/<package>): (The change made/Short description of the change)
+
+[An optional but **highly recommended** commit message describing the changes made in the commit]
+
+[Fixes https://github.com/termux/termux-packages/issues/<issue number>]
+[Closes https://github.com/termux/termux-packages/pull_requests/<pr number>]
+```
+
+- `<commitType>` describes the type of commit. Types of commits:
+ - `upgpkg`: One or more package(s) was/were updated.
+ Optional extended commit message may include new list of features in the new version, and detailed list of changes in build scripts and/or patches
+ - `dwnpkg`: One or more package(s) was/were downgraded due to build issues or potential bugs
+ commit message should include summary of why the package(s) was/were downgraded. If the summary can't completely describe the reason for downgrade, extended commit message should contain full reason for downgrade.
+ - `enhance`: Enable a feature in a package that was earlier not enabled.
+ Optional (but highly recommended) extended commit message may contain detailed summary of the enabled feature(s) and a basic use case
+ - `chore`: Any housekeeping change or a change which does not affect the user in any way.
+ - `rebuild`: Rebuild a package to link against newer version of shared library
+ Special cases:
+ - When mass rebuilding packages depending on a major package (e.g. openssl), consider using this format:
+ ```
+ rebuild(deps:main/openssl): link against OpenSSL 3.0
+ ```
+ - `scripts`: Any change affecting our build scripts
+
+Examples of good commit messages:
+1. ```
+ upgpkg(main/nodejs): upgrade to v18.2.0
+ ```
+
+2. ```
+ dwnpkg(main/htop): downgrade to v2.2.0
+
+ v3.x needs access to /proc/stat which is now restricted by Android
+ ```
+
+3. ```
+ enhance,upgpkg(nodejs): update to v18.2.0 and use shared libuv
+
+ # Describe the technical reasons of how using shared libuv is beneficial
+ ```
+
 ## Basics
 
 Each package is a defined through the `build.sh` script placed into directory