docs: add code completion configuration docs (#2822)

* docs: add code completion configuration docs

* update

website/docs/administration/code-completion.md

@@ -0,0 +1,21 @@
+# Code Completion
+
+Code completion is a key feature offered by Tabby in IDEs/extensions. Tabby allows for more customized configuration by modifying the `config.toml` file in the `[completion]` section.
+
+## Input / Output 
+
+This configuration requires tuning of the model serving configuration as well (e.g., context length settings) and can vary significantly based on the model provider (e.g., llama.cpp, vLLM, TensorRT-LLM, etc).
+Therefore, please only modify these values after consulting with the model deployment vendor.
+
+```toml
+[completion]
+
+# Maximum length of the input prompt, in UTF-8 characters. The default value is set to 1536.
+max_input_length = 1536
+
+# Maximum number of decoding tokens. The default value is set to 64.
+max_decoding_tokens = 64
+```
+
+The default value is set conservatively to accommodate local GPUs and smaller LLMs.
+