docs: improve readme and help message

- Add example for printing output to the terminal
- Fix example for usage as CLI tool (missing -f flag)
- Add instructions in the help message for combining lexers

README.md

@@ -49,9 +49,17 @@ To build from source:
 
 ## Usage as a CLI tool
 
+Show a syntax highlighted version of a C source file in your terminal:
+
+```shell
+$ tartrazine whatever.c -l c -t catppuccin-macchiato --line-numbers -f terminal
+```
+
+Generate a standalone HTML file from a C source file with the syntax highlited:
+
 ```shell
 $ tartrazine whatever.c -l c -t catppuccin-macchiato --line-numbers \
-  --standalone -o whatever.html 
+  --standalone -f html -o whatever.html 
 ```
 
 ## Usage as a Library

src/main.cr

@@ -20,7 +20,8 @@ Usage:
 Options:
   -f <formatter>      Format to use (html, terminal, json)
   -t <theme>          Theme to use, see --list-themes [default: default-dark]
-  -l <lexer>          Lexer (language) to use, see --list-lexers [default: autodetect]
+  -l <lexer>          Lexer (language) to use, see --list-lexers. Use more than
+                      one lexer with "+" (e.g. jinja+yaml) [default: autodetect]
   -o <output>         Output file. Default is stdout.
   --standalone        Generate a standalone HTML file, which includes
                       all style information. If not given, it will generate just