Pin Jekyll version to 4.0.0 (vs 4.0), because 4.0 also matches 4.0.1,…

… which introduced a speed regression jekyll/jekyll#8233 /cc @nqst

CHANGELOG.md

@@ -11,7 +11,7 @@
 ## master
 
 Released: TBA.
-[Diff](https://github.com/kvz/lanyon/compare/v0.2.19...master).
+[Diff](https://github.com/kvz/lanyon/compare/v0.2.20...master).
 
 - [ ] Add a 'real' command line parser for `lib/cli.js` like minimist
 - [ ] Fix bug where failed deploy is not fatal: https://travis-ci.org/kvz/invig/builds/202931498#L627
@@ -21,6 +21,13 @@ Released: TBA.
 - [ ] Throw warning when not jekyll excluding: `- node_modules - .git`, like when you have `exclude: [vendor]` in your jekyll config
 - [ ] Incorporate hacks in tus.io .lanyonrc, it should be able to run with an empty rc, except for hook
 
+## v0.2.20
+
+Released: 2020-06-09
+[Diff](https://github.com/kvz/lanyon/compare/v0.2.19...v0.2.20).
+
+- [x] Pin Jekyll version to 4.0.0 (vs 4.0), because 4.0 also matches 4.0.1, which introduced a speed regression https://github.com/jekyll/jekyll/issues/8233
+
 ## v0.2.19
 
 Released: 2020-06-09

container/Dockerfile

@@ -13,7 +13,7 @@
 # https://rubygems.org/gems/jekyll-last-modified-at
 # https://rubygems.org/gems/jekyll-redirect-from
 
-FROM jekyll/jekyll:4.0
+FROM jekyll/jekyll:4.0.0
 RUN gem install \
     jekyll-archives:2.2.1 \
     stringex:2.8.5 \