✨ add bat completions (#766)

I use it _all the time_!
I am on my way to `rg` completions too, I use it about as often as `bat`

custom-completions/bat/bat-completions.nu

@@ -0,0 +1,64 @@
+# A cat(1) clone with syntax highlighting and Git integration
+export extern "bat" [
+    file?: string  # file to print / concatenate. Use `-` to read from stdin
+    --help         # Print help (see a summary with '-h')
+    -h             # Print help (see more with '--help')
+    --version      # Print version
+    --show-all(-A)         # Show non-printable chars like space, tab and \n
+    --nonprintable-notation: string@"nu-complete nonprintable-notation" # Set notation for non-printable characters
+    --plain(-p)         # Only show plain style, no decorations
+    --language(-l): string@"nu-complete languages" # Explicitly set the language for syntax highlighting
+    --list-languages(-L) # Display a list of supported languages for syntax highlighting
+    --highlight-line: string  # <N:M> Highlight from N to M line range with a different background color
+    --file-name: string # Specify the name to display for a file. Useful when piping data to bat from STDIN when bat does not otherwise know the filename
+    --diff(-d)       # Only show lines that have been added/removed/modified with respect to the Git index. Checkout --diff-context=N
+    --diff-context: number # Include N lines of context around added/removed/modified lines when using '--diff'
+    --tabs: number   # Set the tab width to T spaces. Use a width of 0 to pass tabs through directly
+    --wraps: string@"nu-complete wrap-modes"  # Specify the text-wrapping mode
+    --chop-long-lines(-S) # Truncate all lines longer than screen width. Alias for '--wrap=never'
+    --terminal-width: number # Explicitly set the width of the terminal instead of determining it automatically
+    --number(-n)     # Only show line numbers, no other decorations
+    --color: string@"nu-complete when" # Specify when to use colored output
+    --italic-text: string@"nu-complete ansi italics" # Specify when to use ANSI sequences for italic text in the output
+    --decorations: string@"nu-complete when" # Specify when to use the decorations that have been specified via '--style'
+    --force-colorization(-f) # Alias for '--decorations=always --color=always'
+    --paging: string@"nu-complete when" # Specify when to use the pager
+    --pager: string  # Determine which pager is used
+    --map-syntax(-m): string # <glob:syntax> Map a glob pattern to an existing syntax name
+    --ignored-suffix: string # <ignored-suffix> Ignore extension. For example: 'bat --ignored-suffix ".dev" my_file.json.dev' will use JSON syntax, and ignore '.dev'
+    --theme: string@"nu-complete themes" # Set the theme for syntax highlighting
+    --list-themes    # Display a list of supported themes for syntax highlighting
+    --style: string # Configure which elements (line numbers, file headers, grid borders, Git modifications, ..)
+    --line-range(-r): string # <N:M> Only print from N to M
+    --unbuffered(-u) # This option exists for POSIX-compliance reasons ('u' is for 'unbuffered'). The output is always unbuffered - this option is simply ignored
+    --diagnostic     # Show diagnostic information for bug reports
+    --acknowledgements  # Show acknowledgements
+]
+
+def "nu-complete nonprintable-notation" [] {
+    ['unicode', 'caret']
+}
+
+def "nu-complete languages" [] {
+    ^bat --list-languages 
+    | lines 
+    | parse "{value}:{description}" 
+}
+
+def "nu-complete wrap-modes" [] {
+    ['auto', 'never', 'character']
+}
+
+def "nu-complete when" [] {
+    ['auto', 'never', 'always']
+}
+
+def "nu-complete ansi italics" [] {
+    ['never', 'always']
+}
+
+def "nu-complete themes" [] {
+    ^bat --list-themes 
+    | lines 
+    | parse "{value}" 
+}