docs(faq): add note on (auto)completion

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -8,7 +8,7 @@ body:
  label: Have you read the docs and searched existing issues?
  description: Please check all of the below that are applicable before submitting an issue.
  options:
- - label: I have read [the README's troubleshooting guide](https://github.com/mrcjkb/rustaceanvim/blob/master/README.md#stethoscope-troubleshooting).
+ - label: I have read [the README's troubleshooting guide](https://github.com/mrcjkb/rustaceanvim/blob/master/README.md#stethoscope-troubleshooting) and FAQ(https://github.com/mrcjkb/rustaceanvim?tab=readme-ov-file#left_speech_bubble-faq).
  required: true
  - label: I am using the latest rustaceanvim release.
  required: true

README.md

@@ -867,6 +867,11 @@ and a LSP completion source like [`cmp-nvim-lsp`](https://github.com/hrsh7th/cmp
 This plugin will automatically register the necessary client capabilities
 if you have `cmp-nvim-lsp` installed.
 
+#### I'm having issues with (auto)completion
+
+rustaceanvim doesn't implement (auto)completion.
+Issues with (auto)completion either come from another plugin or rust-analzyer.
+
 #### mason.nvim and nvim-lspconfig
 
 See [`:h rustaceanvim.mason`](./doc/mason.txt) for details about troubleshooting