Fifty Years of Ruby: Initial commit

I waited **way** too long to commit this. I've got most of the slides
added, lots of them close to finished state, lots of presenter notes.

I'm using [Marp](https://marp.app) this time, replacing
[Remark](http://remarkjs.com/).

Fifty-Years-of-Ruby/.tool-versions

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+# Sadly, Marp 4.0 and 3.4 binaries don't support X86; using Homebrew version for now.
+# marp-cli 4.0
+node 20

Fifty-Years-of-Ruby/README.md

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+# Fifty Years of Ruby
+
+This is a talk that I've been thinking about for many years.
+I'll be presenting it ar RubyConf 2024 in Chicago.
+
+I'm using [Marp](https://marp.app) to build my slides.
+This is the first time I'm using it; I used [Remark](https://remarkjs.com) for the past several years.
+
+## Setup
+
+I'm using [mise](https://mise.jdx.dev) now, to install the correct versions of the tools I use.
+Unfortunately, the binaries that the Marp project supplies on GitHub no longer support MacOS on x86-64.
+These are the same binaries that the mise marp-cli plugin uses.
+So I'm currently using Homebrew to install Marp.
+
+~~~ shell
+mise -y install
+brew install --quiet marp-cli
+brew upgrade --quiet marp-cli
+~~~
+
+## Build
+
+To build the HTML page, and have it auto-update as you make changes:
+
+~~~ shell
+marp --config=marp.yml --watch --browser=firefox slides.md -o slides.html
+~~~
+
+To build the HTML page for later use:
+
+~~~ shell
+marp --config=marp.yml slides.md -o slides.html
+~~~
+
+To create a PDF:
+
+~~~ shell
+marp --config=marp.yml --pdf --preview slides.md -o slides.pdf
+~~~
+
+## TODO
+
+1. Questions for dry-run
+    - Should I just put everything in chronological order?
+    - Should I put the RubyConf graphic on most slides?
+    - Note these TODOs
+    - Suggestions for better transitions
+    - Suggestions for better pictures
+    - Should I include full dates, or just years?
+2. Language support for Faux-O
+    - Bob Martin said that the only thing that has changed in the last 50 years has been adding constraints
+        - Structured programming constrains use of GOTO
+        - Object-oriented programming constrains use of global variables
+        - Functional programming constrains use of assignment
+        - Declarative programming constrains use of control structures
+    - I think a language that gives us Faux-O constraints is next
+        - Why not both OO and FP support in a language?
+            - Ruby, Smalltalk, and JavaScript do this fairly well
+        - I believe we need immutable objects that are around passed to functions
+            - Manipulate them with function calls, rather than message passing
+            - But the syntax looks the same as OO
+            - They can **represent** a state instead of **having** a state
+        - Message-passing actors for the procedural shell
+3. Compile-time execution will continue to gain popularity
+    - Today: you tell it what should run at compile time
+    - Future: let the compiler run whatever it thinks is best
+4. Slide: XR, new Meta concept, Apple XR, Oculus, etc
+5. Slide about Mac?
+6. Make Headings stay at the top of the page consistently
+7. Fix colors in header/footers
+8. Add "RubyConf 2024" to title page
+9. Make quotes look nicer
+10. Add a header with the date?
+    - or the title
+    - or RubyConf 2024
+11. Create a thumbnail of the presentation
+    - `marp --image=png slides.md -o og-image.png`
+    - generate slide-show with `--og-image=og-image.png`
+    - or add `image: og-image.png` to marp.yml
+12. Makefile?

Fifty-Years-of-Ruby/marp.yml

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+theme: slides.css
+template: bespoke
+bespoke:
+  osc: false # Don't show on-screen controls.
+  progress: true # Show a progress bar in the top few pixels of the window.
+  transition: true # Allow transition animations between slides.
+options:
+  emoji:
+    unicode: false # Don't use Twemoji (because it hits the Internet).
+    shortcode: true # Convert shortcodes (like `:dog:`) to Unicode (🐶).
+pdfNotes: true # Include notes in PDFs.
+pdfOutlines:
+  pages: false
+  headings: true
+allowLocalFiles: true # Allow PDF converter to read local (relative) files. (WARNING: Potentially insecure.)

Fifty-Years-of-Ruby/slides.css

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+@theme "boochtek";
+@import-theme "default";
+
+/* Page numbers in right footer. */
+section::after {
+    content: attr(data-marpit-pagination) " / " attr(data-marpit-pagination-total);
+}
+header,
+footer,
+section::after {
+    font-size: 20px;
+    padding: 0 1ex;
+    background: rgba(240, 240, 240, 0.5);
+}
+
+section.title h1 {
+    font-size: 100px;
+    color: rgb(242, 149, 16);
+}
+
+img[src="assets/RubyConf-2024-background-doodle-2.png"] {
+    position: absolute;
+    top: 0;
+    right: 0;
+    width: 300px;
+}
+
+.columns {
+    display: grid;
+    grid-template-columns: repeat(2, minmax(0, 1fr));
+    gap: 1rem;
+}