add fallback raster images for social tags

_includes/default_head_tags.html

@@ -19,7 +19,14 @@
 
 <meta property="og:type" content="website">
 
-{% if page.image %}
+{% if page.social_image %}
+{% assign image = page.social_image %}
+{% elsif page.image %}
+{% assign image = page.image %}
+{% else image = false %}
+{% endif %}
+
+{% if image %}
 <!--  This tag enables pages to be featured in Google Discover as large previews
 See: https://developers.google.com/search/docs/advanced/mobile/google-discover?hl=en&visit_id=637424198370039526-3805703503&rd=1 -->
 <meta name="robots" content="max-image-preview:large">

_posts/2022-05-20-conda_setup.md

@@ -2,7 +2,6 @@
 title:  My Jupyter and Conda setup
 date: 2022-02-02
 layout: post
-image:
 ---
 
 I really like working in Jupyterlab but getting it to work nicely is always a bit challenging, these are my notes for roughly how I have it set up.

_posts/2022-11-10-adding_interactivity_to_svg.md

@@ -2,7 +2,8 @@
 title: How to Animate Inkscape SVGs with d3
 excerpt: In which a simple thing turns out to be surprisingly in-depth!
 layout: post
-image: /assets/extracted_from_ipynb/452af1f7-a8e3-4b32-b6d2-720c31f27af3.png
+image: /assets/thesis/intro_chapter/fk_schematic.svg
+social_image: /assets/social/fk_diagram.png
 alt: A diagram showing showing circles with arrows in them linked by lines that represents a simple physical model of electron spins interacting.
 ---
 

_posts/2022-11-22-sensor_watch.md

@@ -2,6 +2,7 @@
 title:  Sensor Watch
 layout: post
 image: /assets/blog/SensorWatch/watch.svg
+social_image: /assets/social/sensor_watch.svg
 alt: A simple vector image of a classic casio watch.
 ---
 

_posts/2022-11-23-emscripten_arduino.md

@@ -2,6 +2,7 @@
 title:  Using emscripten to simulate an arduino project
 layout: post
 image: /assets/blog/emscripten_arduino/arduino.svg
+social_image: /assets/social/arduino.png
 alt: A rendered image of a breadboard with an LED and resistor wired up in series to an arduino.
 ---
 

_posts/2023-02-10-shelves.md

@@ -3,6 +3,7 @@ title: Fantasy Ikea Shelves
 excerpt: We needed some shelves to fit an odd space under a ladder...
 layout: post
 image: /assets/blog/shelves/thumb.svg
+social_image: /assets/social/shelves.png
 alt: A 3D render of some shelves fitting into a triangular space under a ladder.
 ---
 In our new flat we have this mezzanine bed with a yellow ladder leading up to it. Between the ladder and the wardrobe we had this kind of triangular space that we wanted to use for more storage. After doing a quick design on paper I started mocking something up. 

_posts/2023-06-20-conda_setup.md

@@ -3,6 +3,8 @@ title:  Jupyter and Conda setup
 date: 2023-06-20
 layout: post
 image: /assets/blog/mamba/logos.svg
+social_image: /assets/social/jupyter.png
+alt: The orange, abstract, Jupyter logo and the Mamba logo which is a cute black snake.
 ---
 
 These are my notes to myself about how to setup jupyter+conda/mamba environments.

_posts/2023-06-21-my_first_PCB.md

@@ -5,7 +5,7 @@ excerpt: |
 layout: post
 commentid: 110810437631337327
 hide_image: true # Only use this image for static previews
-image: /assets/blog/PCB/horizontal.png
+social_image: /assets/social/pcb_1.png
 alt: A 3D render of a simple PCB.
 ---
 I made my first PCB!

_posts/2023-07-20-writing_grammars_is_fun.md

@@ -16,6 +16,8 @@ excerpt: |
 
     >>> ('a', 'b', 'c')
     ```
+social_image: /assets/social/parsing.png
+alt: A screenshot of some python code showing a PEG grammar definition.
 layout: post
 commentid: 110746239432993930
 ---