feat: Add syntax highlight file for GNU nano (#4560)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

grammars/nano/README.md

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+# Syntax highlighting for GNU nano
+
+This is a syntax highlighting file the [GNU nano](https://nano-editor.org/) text
+editor.
+
+## Installation
+
+To install place the `prql.nanorc` file in the `~/.nano/` directory and and
+include the following line in your `.nanorc` file.
+
+    include "~/.nano/prql.nanorc"
+
+You can append it with this command:
+
+    echo 'include "~/.nano/prql.nanorc"' >> ~/.nanorc

grammars/nano/prql.nanorc

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+## Syntax highlighting for PRQL.
+
+syntax python "\.prql$"
+magic "PRQL script"
+comment "#"
+
+# Types.
+color green "\<(int(8|16|32|64|128)?|float(32|64)|bool|text|date|time|timestamp)\>"
+
+# Keywords.
+color yellow "\<let|module|prql\>"
+
+# Transforms.
+color brightcyan "\<(aggregate|derive|filter|from|group|join|select|sort|take|window)\>"
+
+# Special values.
+color brightmagenta "\<(false|null|true|this|that)\>"
+
+# Decorators.
+color cyan start="@\{" end="\}"
+
+# Mono-quoted strings.
+color brightgreen "[frs]?'([^'\]|\\.)*'|[frs]?"([^"\]|\\.)*"|'''|""""
+color normal "'''|""""
+# Comments.
+color gray "(^|[[:blank:]])#.*"
+# Triple-quoted strings.
+color brightgreen start="[frs]?'''([^'),]|$)" end="(^|[^(\])'''"
+color brightgreen start="[frs]?"""([^"),]|$)" end="(^|[^(\])""""
+
+# Backslash escapes.
+color lime "\\($|[\'"bfnrt]|[0-3]?[0-7]?[0-7]|x[[:xdigit:]]{2})"
+color lime "\\(N\{[[:alpha:]]+\}|u\{[[:xdigit:]]{1,6}\})"
+
+# Reminders.
+color brightwhite,yellow "\<(FIXME|TODO)\>"
+
+# Trailing whitespace.
+color ,green "[[:space:]]+$"