README.md, themes/boxgruv, .gitmodules: commit to using terminal as my theme, no longer have a separate branch for it, remove boxgruv theme

.gitmodules

@@ -1,6 +1,3 @@
 [submodule "themes/terminal"]
 	path = themes/terminal
 	url = https://git.revsuine.xyz/revsuine/hugo-theme-terminal.git
-[submodule "themes/boxgruv"]
-	path = themes/boxgruv
-	url = https://git.revsuine.xyz/revsuine/hugo-theme-boxgruv.git

README.md

@@ -1,7 +1,7 @@
 # revsuine.xyz Website
 
 These are the markdown files used to build [my website](https://revsuine.xyz/) with [Hugo](https://gohugo.io/). The
-live website is currently built off of the `terminal` branch.
+website uses [panr's Terminal theme](https://github.com/panr/hugo-theme-terminal).
 
 ## Style
 
@@ -9,17 +9,6 @@ Lines have a character limit of 120 where possible.
 
 ## Theming
 
-### Theme Branches
-
-I have branches for each theme for the website. Commits to `master` should be theme-independent commits, e.g. new
-posts. Theme branches should pull from `master` whenever there are new `master` commits. Commits exclusive to theme
-branches should *only* be for changes relevant to the theme.
-
-Theme branches are what should be used to build the website. `master` should not be used for building/deployment, only
-to store common changes among all branches.
-
-### [Terminal](https://github.com/panr/hugo-theme-terminal)
-
 Colours taken from [gruvbox-material medium](https://github.com/sainnhe/gruvbox-material).
 
 | Element    | Colour    |

themes/boxgruv

@@ -1 +0,0 @@
-Subproject commit 3225b22c0403b217257193211e65f3eded4be70e