doc: fix display of "problematic" ASCII characters

When preparing output for a terminal that supports Unicode, Groff remaps
the following characters to typographically "fancier" versions:

    ^ (U+005E)  ->  ˆ (U+02C6)
    ~ (U+007E)  ->  ˜ (U+02DC)
    - (U+002D)  ->  ‐ (U+2010)
    ` (U+0060)  ->  ‘ (U+2018)
    ' (U+0027)  ->  ’ (U+2019)

This transformation is normally desirable in high-quality typeset output
(PDF and PostScript), but frequently problematic in terminal display. As
described in groff_char(7), the following escape sequences are needed to
display the aforementioned characters as they appear in source code:

    ^   ->   \(ha   (Mnemonic: "hat")
    ~   ->   \(ti   (Mnemonic: "tilde")
    -   ->   \-
    `   ->   \(ga   (Mnemonic: "grave accent")
    '   ->   \(aq   (Mnemonic: "apostrophe quote")

These constructs are cumbersome to write, obstruct readability of source
code, and are completely opaque to the majority of man page authors (who
only care about terminal display). A simpler solution is to use `.tr` to
translate these characters automatically.

PR-URL: #44373
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/node.1

@@ -26,6 +26,7 @@
 .\"
 .\"======================================================================
 .
+.tr -\-^\(ha~\(ti`\(ga
 .Dd 2018
 .Dt NODE 1
 .