Add more tests of lexer's skipToLeadingKeyword behavior (#1971)

The character after the ending keyword gets blue-painted.

test/asm/expansion-after-end.asm

@@ -0,0 +1,25 @@
+DEF x = 0
+DEF s EQUS "\nprintln \"lol\", x\ndef x += 1"
+
+if 0
+	println "no"
+endc{#s}
+
+if 1
+	println "yes"
+else{#s}
+	println "nope"
+endc{#s}
+
+rept 0
+	println "no way"
+endr{#s}
+
+println "x = ", x
+
+MACRO m
+	if 0
+		println "no how"
+	endc\1
+ENDM
+m \nprintln "haha"

test/asm/expansion-after-end.err

@@ -0,0 +1,24 @@
+error: Invalid character '{'
+    at expansion-after-end.asm(6)
+error: syntax error, unexpected symbol, expecting end of line or end of buffer or end of fragment literal
+    at expansion-after-end.asm(6)
+error: Invalid character '}'
+    at expansion-after-end.asm(6)
+error: Invalid character '{'
+    at expansion-after-end.asm(12)
+error: syntax error, unexpected symbol, expecting end of line or end of buffer or end of fragment literal
+    at expansion-after-end.asm(12)
+error: Invalid character '}'
+    at expansion-after-end.asm(12)
+error: Invalid character '{'
+    at expansion-after-end.asm(16)
+error: syntax error, unexpected symbol, expecting end of line or end of buffer or end of fragment literal
+    at expansion-after-end.asm(16)
+error: Invalid character '}'
+    at expansion-after-end.asm(16)
+error: Invalid character '1' after line continuation
+    at expansion-after-end.asm::m(23) <- expansion-after-end.asm(25)
+error: syntax error, unexpected number, expecting end of line or end of buffer or end of fragment literal
+    at expansion-after-end.asm::m(23) <- expansion-after-end.asm(25)
+FATAL: Ended block with 1 unterminated conditional (`IF`/`ELIF`/`ELSE` block)
+    at expansion-after-end.asm::m(24) <- expansion-after-end.asm(25)

test/asm/expansion-after-end.out

@@ -0,0 +1,2 @@
+yes
+x = $0

test/asm/interpolate-else.asm

@@ -0,0 +1,13 @@
+def hmm equs "else"
+
+if 1
+	println "yes"
+{hmm}
+	println "no"
+endc
+
+if 0
+	println "NO"
+{hmm}
+	println "YES"
+endc

test/asm/interpolate-else.out

@@ -0,0 +1 @@
+yes

test/asm/leading-keywords.asm

@@ -0,0 +1,20 @@
+; This covers some edge cases of `skipToLeadingKeyword`
+
+SECTION "test", ROM0
+
+MACRO mac
+	if 1
+		DEF x = \1_WIDTH
+		DEF y = \1_HEIGHT
+	elif 0
+		DEF x = \1_HEIGHT
+		DEF y = \1_WIDTH
+	else
+		fail "nope"
+	endc
+	db \1_WIDTH, \1_HEIGHT, x, y
+ENDM
+
+	DEF NAME_WIDTH EQU 10
+	DEF NAME_HEIGHT EQU 9
+	mac NAME

test/asm/leading-keywords.out.bin

@@ -0,0 +1,3 @@
+
+	
+