Add 7.3.0 changelog (#2080)

* Add changelog

* Fix spellcheck

* Fix markdown style

* Fix markdown

* Fix headings

* Fix markdown spaces

* Fix markdown spaces

* Fix more

* Split lines

---------

Co-authored-by: Denis Spitsyn <denis.spitsyn.nct@gmail.com>

.aspell.en.pws

@@ -79,6 +79,8 @@ CHIINV
 chinese
 CHISQ
 CHITEST
+CHOOSECOLS
+CHOOSEROWS
 citus
 CJK
 clientLog
@@ -151,6 +153,7 @@ DocumentServer
 docx
 Docx
 DOCX
+DOCXF
 DOTX
 downloadAs
 dPc
@@ -222,6 +225,7 @@ getLocale
 GetName
 GetPageOrientation
 GetPosInParent
+GetRange
 GetRightMargin
 GetRowHeight
 GetRows
@@ -253,6 +257,7 @@ hotkeys
 html
 htmlutils
 https
+HSTACK
 hy
 HYPGEOM
 icu
@@ -290,10 +295,12 @@ jpeg
 js
 JS
 json
+jsonwebtocken
 jwt
 JWT
 korean
 lang
+LaTeX
 LeftMargin
 leftMenu
 libcurl
@@ -308,6 +315,7 @@ LOGEST
 LOGNORM
 logrotate
 lookup
+lool
 LOOL
 LTS
 macOS
@@ -321,6 +329,7 @@ Mendeley
 MergeArea
 metadata
 metafile
+metafiles
 México
 mht
 MINIFS
@@ -510,22 +519,30 @@ statsd
 statusBar
 STDEV
 stirkeout
+substring
 SUMIFS
 SUMPRODUCT
+supervisord
 sv
 Svenska
 Sverige
 svg
 SVG
 Svizzera
+systemd
 tabSelected
 TDIST
+TEXTAFTER
+TEXTBEFORE
 TEXTJOIN
+TEXTSPLIT
 textPoweredBy
 thai
 TINV
 TOC
+TOCOL
 toLocaleString
+TOROW
 toolbarNoTabs
 tooltip
 tooltips
@@ -560,6 +577,7 @@ UTF
 util
 verysilent
 VLOOKUP
+VSTACK
 vml
 wav
 WEIBULL
@@ -569,6 +587,8 @@ wmf
 WOPI
 WordControl
 WrapText
+WRAPCOLS
+WRAPROWS
 xfIndexNumber
 XLOOKUP
 xls