bug#44267: New input method 'compose'

[Juri Linkov]

>> +(quail-define-package
>> + "compose" "UTF-8" "+" t
>
> I think "UTF-8" is not the best name for this.  How about "Unicode"?

This input method was based on the existing Unicode input methods
"TeX", "rfc1345", "sgml" that all use "UTF-8".  And `M-x list-input-methods'
puts all them under the "UTF-8" category.

> This new method should be called out in NEWS.

Maybe something like this:

diff --git a/etc/NEWS b/etc/NEWS
index 24f0acf0fb..b4b9e87499 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -129,6 +129,9 @@ Emacs to break lines after more characters than just 
whitespace
 characters.  In particular, this significantly improves word-wrapping
 for CJK text mixed with Latin text.
 
+---
+** New input method 'compose' based on X Multi_key sequences.
+
 ---
 ** Improved language transliteration in Malayalam input methods.
 Added a new Mozhi scheme.  The inapplicable ITRANS scheme is now