v1.3.0-pre.2

highlights:

• Go+ Specification for STEM Education (mini spec)

docs:

• Go+ Specification for STEM Education (#1943 #1944 #1945 #1946 #1947 #1948 #1950 #1952 #1955 #1956 #1968 #1969 #1970 #1971 #1972 #1974 #1976 #1977)
• README: How Go+ simplifies Go's expressions (#1941 #1953 #1957 #1973)

changes:

• mod: rollback golang.org/x/tools v0.22.0 => v0.19.0 (#1966)
• mod: github.com/goplus/llgo v0.9.7
• cl: fix slicelit for assignStmt/returnStmt (#1959)
• cl: fix compositeLit for assignStmt (#1960)
• cl: fix compileCompositeLitEx struct for sliceLit/mapLit (#1961)