Implement text-mode-first syntax (#500)

* Implement text-mode-first syntax

Following the 2023-10-23 teleconference, implement "option 2a with additional ugliness".

(This PR is not yet ready for review. It will include updating the syntax.md.)

* Update syntax.md

* Update formatting.md

* Update README.md

- includes the local / input change

* Fix some minor formatting

* Un-aligning rule `=` signs

* Update spec/syntax.md

Co-authored-by: Eemeli Aro <[email protected]>

* Update registry.md

* Update registry.md

* Fix some message formatting

* Missing example in The Message

* Fix `pattern` ABNF and add `quoted-pattern` ABNF to syntax

* Fix English for `quoted-pattern`

* Fix text about quoting whitespace in `text`

* Update spec/syntax.md

Co-authored-by: Eemeli Aro <[email protected]>

---------

Co-authored-by: Eemeli Aro <[email protected]>

Author: aphillips

README.md

@@ -17,40 +17,44 @@ The syntax is formally described in [ABNF](spec/message.abnf).
 
 Messages can be simple strings:
 
-    {Hello, world!}
+    Hello, world!
 
 Messages can interpolate arguments formatted using _formatting functions_:
 
-    {Today is {$date :datetime weekday=long}.}
+    Today is {$date :datetime weekday=long}.
 
 Messages can define variants which correspond to the grammatical (or other) requirements of the language:
 
+    {{
     match {$count :number}
-    when 1 {You have one notification.}
-    when * {You have {$count} notifications.}
+    when 1 {{You have one notification.}}
+    when * {{You have {$count} notifications.}}
+    }}
 
 The message syntax is also capable of expressing more complex translation, for example:
 
-    let $hostName = {$host :person firstName=long}
-    let $guestName = {$guest :person firstName=long}
-    let $guestsOther = {$guestCount :number offset=1}
+    {{
+    local $hostName = {$host :person firstName=long}
+    local $guestName = {$guest :person firstName=long}
+    local $guestsOther = {$guestCount :number offset=1}
 
     match {$host :gender} {$guestOther :number}
 
-    when female 0 {{$hostName} does not give a party.}
-    when female 1 {{$hostName} invites {$guestName} to her party.}
-    when female 2 {{$hostName} invites {$guestName} and one other person to her party.}
-    when female * {{$hostName} invites {$guestName} and {$guestsOther} other people to her party.}
-
-    when male 0 {{$hostName} does not give a party.}
-    when male 1 {{$hostName} invites {$guestName} to his party.}
-    when male 2 {{$hostName} invites {$guestName} and one other person to his party.}
-    when male * {{$hostName} invites {$guestName} and {$guestsOther} other people to his party.}
-
-    when * 0 {{$hostName} does not give a party.}
-    when * 1 {{$hostName} invites {$guestName} to their party.}
-    when * 2 {{$hostName} invites {$guestName} and one other person to their party.}
-    when * * {{$hostName} invites {$guestName} and {$guestsOther} other people to their party.}
+    when female 0 {{{$hostName} does not give a party.}}
+    when female 1 {{{$hostName} invites {$guestName} to her party.}}
+    when female 2 {{{$hostName} invites {$guestName} and one other person to her party.}}
+    when female * {{{$hostName} invites {$guestName} and {$guestsOther} other people to her party.}}
+
+    when male 0 {{{$hostName} does not give a party.}}
+    when male 1 {{{$hostName} invites {$guestName} to his party.}}
+    when male 2 {{{$hostName} invites {$guestName} and one other person to his party.}}
+    when male * {{{$hostName} invites {$guestName} and {$guestsOther} other people to his party.}}
+
+    when * 0 {{{$hostName} does not give a party.}}
+    when * 1 {{{$hostName} invites {$guestName} to their party.}}
+    when * 2 {{{$hostName} invites {$guestName} and one other person to their party.}}
+    when * * {{{$hostName} invites {$guestName} and {$guestsOther} other people to their party.}}
+    }}
 
 See more examples and the formal definition of the grammar in [spec/syntax.md](./spec/syntax.md).