DOC: add notebook for Lecture 18 (#11)

Source: https://indico.ific.uv.es/event/6803/contributions/21235

* DOC: add Google Colab badge for whole repository
* FIX: let data hash depend on notebooks
* FIX: remove `gdown` install cell from HTML pages

.github/workflows/docs.yml

@@ -31,9 +31,9 @@ jobs:
       - name: Fetch downloaded data
         uses: actions/cache@v3
         with:
-          key: data-${{ hashFiles('docs/data/') }}
+          key: data-${{ hashFiles('docs/**.ipynb') }}
           restore-keys: |
-            data-${{ hashFiles('docs/data/') }}
+            data-${{ hashFiles('docs/**.ipynb') }}
             data
           path: |
             ./docs/data

.gitignore

@@ -7,3 +7,5 @@ ExtendedLLexample.txt
 _build/
 condaenv.*.requirements.txt
 data/
+docs/example.txt
+docs/lecture18

README.md

@@ -1,5 +1,6 @@
 # STRONG2020 HaSP School
 
+[![Google Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/ComPWA/strong2020-salamanca/blob/main)
 [![GitHub Pages](https://github.com/ComPWA/strong2020-salamanca/actions/workflows/docs.yml/badge.svg)](https://github.com/ComPWA/strong2020-salamanca/actions/workflows/docs.yml)
 
 This (unofficial) repository contains the exercises for the [STRONG2020 HaSP School](https://indico.ific.uv.es/event/6803) which was organised in Salamanca in 2023. Many of the files hosted in this repository originate from the [lecture material](https://indico.ific.uv.es/event/6803/timetable).

docs/lecture02.ipynb

@@ -40,7 +40,11 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "metadata": {},
+   "metadata": {
+    "tags": [
+     "remove-cell"
+    ]
+   },
    "outputs": [],
    "source": [
     "%pip install -q gdown"