html/template: set division context when a template literal closes

[harjothkhara]

A '/' that follows a JavaScript template literal starts a division,
not a regexp literal, but tJSTmpl left jsCtx unchanged when it saw
the closing backtick. The context stayed jsCtxRegexp from when the
literal opened, so a template action after the literal was escaped
as regexp text and its value was written without quotes:

<script>let x = `a`/{{.}}/b;</script>

executed with the value "alert1" produced

<script>let x = `a`/alert`1`/b;</script>

Set jsCtx to jsCtxDivOp when the closing backtick is reached, the
same way tJSDelimited does when a JS string or regexp closes.

Fixes #81117

[gopherbot]

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[gopherbot]

Message from Gopher Robot:

Patch Set 1:

(1 comment)

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