Add intructions for query running

Author: sylwia-budzynska

CodeQL_Queries/README.md

@@ -0,0 +1,19 @@
+To run the queries in this repository:
+1. Click the green "Code" button > Codespaces > Create a codespace on main. A new codespace will be created for you with VS Code CodeQL extension preinstalled.
+2. When the codespace finishes setting up, open the terminal, and find the path to the codeql binary (which comes preinstalled with the VS Code CodeQL extension) with the command:
+```bash
+find ~ -type f -name codeql -executable 2>/dev/null
+```
+It will most likely look similar to this:
+```
+/home/codespace/.vscode-remote/data/User/globalStorage/github.vscode-codeql/distribution1/codeql/codeql
+```
+3. Using the CodeQL binary, go to the language folder with the query you want to run `codeql pack install, for example:
+```bash
+cd cpp
+/home/codespace/.vscode-remote/data/User/globalStorage/github.vscode-codeql/distribution1/codeql/codeql pack install
+```
+This will install the CodeQL library files required to run the CodeQL queries.
+4. Press `Ctrl/Cmd + Shift + R` to reload the window to see syntax highlighting etc. 
+5. Check the README in the folder with the query you are interested in, and add the database listed in the README to your VS Code CodeQL extension.
+6. Open the query file you are interested in, right-click and choose `CodeQL: Run Query on selected database` from the dropdowns.