preguide: rework preguide schema

With a number of recent changes/improvements in CUE we can greatly
simplify the preguide schema. This also serves as preparation for
changes that will be made as part of #64.

For #115

go.mod

@@ -3,7 +3,7 @@ module github.com/play-with-go/preguide
 go 1.15
 
 require (
-	cuelang.org/go v0.3.0-beta.5.0.20210217114833-77e6b51a0f14
+	cuelang.org/go v0.3.0-beta.5.0.20210217114852-2c86835c2019
 	github.com/gohugoio/hugo v0.69.2
 	github.com/google/go-cmp v0.4.0
 	github.com/jteeuwen/go-bindata v3.0.7+incompatible

go.sum

@@ -9,6 +9,8 @@ contrib.go.opencensus.io/integrations/ocsql v0.1.4/go.mod h1:8DsSdjz3F+APR+0z0Wk
 contrib.go.opencensus.io/resource v0.0.0-20190131005048-21591786a5e0/go.mod h1:F361eGI91LCmW1I/Saf+rX0+OFcigGlFvXwEGEnkRLA=
 cuelang.org/go v0.3.0-beta.5.0.20210217114833-77e6b51a0f14 h1:+1eo+JhIIgnJ/8i4x22ENq9pEchFZMEJTSUDW7mGM30=
 cuelang.org/go v0.3.0-beta.5.0.20210217114833-77e6b51a0f14/go.mod h1:Ikvs157igkGV5gFUdYSFa+lWp/CDteVhubPTXyvPRtA=
+cuelang.org/go v0.3.0-beta.5.0.20210217114852-2c86835c2019 h1:mj5d8fHqqDGVAeGwO5FeLsYAOIYL+ifjySl0v18NVyo=
+cuelang.org/go v0.3.0-beta.5.0.20210217114852-2c86835c2019/go.mod h1:Ikvs157igkGV5gFUdYSFa+lWp/CDteVhubPTXyvPRtA=
 dmitri.shuralyov.com/gpu/mtl v0.0.0-20201218220906-28db891af037/go.mod h1:H6x//7gZCb22OMCxBHrMx7a5I7Hp++hsVxbQ4BYO7hU=
 github.com/Azure/azure-amqp-common-go v1.1.3/go.mod h1:FhZtXirFANw40UXI2ntweO+VOkfaw8s6vZxUiRhLYW8=
 github.com/Azure/azure-amqp-common-go v1.1.4/go.mod h1:FhZtXirFANw40UXI2ntweO+VOkfaw8s6vZxUiRhLYW8=
@@ -334,6 +336,7 @@ golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8U
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190731235908-ec7cb31e5a56/go.mod h1:JhuoJpWY28nO4Vef9tZUw9qufEGTyX1+7lmHxV5q5G4=
+golang.org/x/exp v0.0.0-20210126221216-84987778548c h1:sWZb7hc7UoMhB5/VYk5+nsHuiHq8J5l0osfBYs9C3gw=
 golang.org/x/exp v0.0.0-20210126221216-84987778548c/go.mod h1:I6l2HNBLBZEcrOoCpyKLdY2lHoRZ8lI4x60KMCQDft4=
 golang.org/x/image v0.0.0-20190227222117-0694c2d4d067/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
 golang.org/x/image v0.0.0-20190802002840-cff245a6509b/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=